Topic Editors

Dr. Paolo Restuccia
Department of Chemistry and Institute for Molecular Science and Engineering, Imperial College London, White City Campus, 80 Wood Lane, London W12 0BZ, UK
Prof. Dr. James Ren
School of Engineering, Liverpool John Moores University, Liverpool L3 3AF, UK

First-Principles Simulation—Nano-Theory

Abstract submission deadline
closed (20 May 2022)
Manuscript submission deadline
closed (20 August 2022)
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Topic Information

Dear Colleagues,

First-principles calculation is the most powerful theoretical tool for investigating the atomistic structure of materials. Today, it is being used as a standard tool of material research covering several branches of science and technology, such as atomic and molecular sciences, pharmacy, polymer chemistry and physics, condensed matter physics minerology, and nanotechnology. First-principles calculation is based on quantum mechanics, which was established in the 1930s but is still undergoing evolution, thanks to the rapid development of supercomputers and new theories for the treatment of numerous electron systems at the desired accuracy and within reasonable computation times. First-principles calculation is rapidly broadening its application fields and enabling study of several kinds of material and nanostructure which, until recently, had been impossible to simulate. We invite researchers to contribute to the Special Issue “First-Principles Simulation—Nano-Theory”, which intends to serve as a unique multidisciplinary forum covering broad aspects of the science, technology, and applications of first-principles simulations. The potential topics include, but are not limited to: - New theory of first-principles simulation; - Development of first-principles calculation code; - Computer science of first-principles calculation; - Simulation of molecules, solids, condensed matter, minerals, surfaces, and nanostructures; - Simulation of nanodevices; - Simulation of soft matter; - Chemical and pharmaceutical applications of first-principles simulation.

Dr. Paolo Restuccia
Prof. Dr. James Ren
Topic Editors

Keywords

  • first-principles simulation, theory, program
  • computer science
  • material and device research

Participating Journals

Journal Name Impact Factor CiteScore Launched Year First Decision (median) APC
Crystals
crystals
2.670 3.2 2011 11.2 Days 2000 CHF
Eng
eng
- - 2020 26.6 Days 1000 CHF
Materials
materials
3.748 4.7 2008 15.3 Days 2300 CHF
Chemistry
chemistry
- - 2019 16.1 Days 1400 CHF
Nanoenergy Advances
nanoenergyadv
- - 2021 15.0 days * 1000 CHF

* Median value for all MDPI journals in the first half of 2022.


Preprints is a platform dedicated to making early versions of research outputs permanently available and citable. MDPI journals allow posting on preprint servers such as Preprints.org prior to publication. For more details about reprints, please visit https://www.preprints.org.

Published Papers (27 papers)

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Article
Mott Insulator Ca2RuO4 under External Electric Field
Materials 2022, 15(19), 6657; https://doi.org/10.3390/ma15196657 - 26 Sep 2022
Abstract
We have investigated the structural, electronic and magnetic properties of the Mott insulator Ca2RuO4 under the application of a static external electric field in two regimes: bulk systems at small fields and thin films at large electric fields. Ca2 [...] Read more.
We have investigated the structural, electronic and magnetic properties of the Mott insulator Ca2RuO4 under the application of a static external electric field in two regimes: bulk systems at small fields and thin films at large electric fields. Ca2RuO4 presents S- and L-Pbca phases with short and long c lattice constants and with large and small band gaps, respectively. Using density functional perturbation theory, we have calculated the Born effective charges as response functions. Once we break the inversion symmetry by off-centering the Ru atoms, we calculate the piezoelectric properties of the system that suggest an elongation of the system under an electric field. Finally, we investigated a four-unit cell slab in larger electric fields, and we found insulator–metal transitions induced by the electric field. By looking at the local density of states, we have found that the gap gets closed on surface layers while the rest of the sample is insulating. Correlated to the electric-field-driven gap closure, there is an increase in the lattice constant c. Regarding the magnetic properties, we have identified two phase transitions in the magnetic moments with one surface that gets completely demagnetized at the largest field investigated. In all cases, the static electric field increases the lattice constant c and reduces the band gap of Ca2RuO4, playing a role in the competition between the L-phase and the S-phase. Full article
(This article belongs to the Topic First-Principles Simulation—Nano-Theory)
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Article
Effects of Mono-Vacancies and Co-Vacancies of Nitrogen and Boron on the Energetics and Electronic Properties of Heterobilayer h-BN/graphene
Materials 2022, 15(18), 6369; https://doi.org/10.3390/ma15186369 - 14 Sep 2022
Abstract
A study is carried out which investigates the effects of the mono-vacancies of boron (VB) and nitrogen (VN) and the co-vacancies of nitrogen (N), and boron (B) on the energetics and the structural, electronic, and magnetic properties of an h-BN/graphene heterobilayer using first-principles [...] Read more.
A study is carried out which investigates the effects of the mono-vacancies of boron (VB) and nitrogen (VN) and the co-vacancies of nitrogen (N), and boron (B) on the energetics and the structural, electronic, and magnetic properties of an h-BN/graphene heterobilayer using first-principles calculations within the framework of the density functional theory (DFT). The heterobilayer is modelled using the periodic slab scheme. In the present case, a 4 × 4-(h-BN) monolayer is coupled to a 4 × 4-graphene monolayer, with a mismatch of 1.40%. In this coupling, the surface of interest is the 4 × 4-(h-BN) monolayer; the 4 × 4-graphene only represents the substrate that supports the 4 × 4-(h-BN) monolayer. From the calculations of the energy of formation of the 4 × 4-(h-BN)/4 × 4-graphene heterobilayer, with and without defects, it is established that, in both cases, the heterobilayers are energetically stable, from which it is inferred that these heterobilayers can be grown in the experiment. The formation of a mono-vacancy of boron (1 VB), a mono-vacancy of nitrogen (1 VN), and co-vacancies of boron and nitrogen (VBN) induce, on the structural level: (a) for 1 VB, a contraction n of the B-N bond lengths of ~2.46% and a slight change in the interfacial distance D (~0.096%) with respect to the heterobilayer free of defects (FD) are observed; (b) for 1 VN, a slight contraction of the B-N of bond lengths of ~0.67% and an approach between the h-BN monolayer and the graphene of ~3.83% with respect to the FD heterobilayer are observed; (c) for VBN, it can be seen that the N-N and B-B bond lengths (in the 1 VB and 1 VN regions, respectively) undergo an increase of ~2.00% and a decrease of ~3.83%, respectively. The calculations of the Löwdin charge for the FD heterobilayer and for those with defects (1 VB, 1 VN, and VBN) show that the inclusion of this type of defect induces significant changes in the Löwdin charge redistribution of the neighboring atoms of VB and VN, causing chemically active regions that could favor the interaction of the heterobilayer with external atoms and/or molecules. On the basis of an analysis of the densities of states and the band structures, it is established that the heterobilayer with 1 VB and VBN take on a half-metallic and magnetic behavior. Due to all of these properties, the FD heterobilayer and those with 1 VB, 1 VN, and VBN are candidates for possible adsorbent materials and possible materials that could be used for different spintronic applications. Full article
(This article belongs to the Topic First-Principles Simulation—Nano-Theory)
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Article
Thermal Expansion of 3C-SiC Obtained from In-Situ X-ray Diffraction at High Temperature and First-Principal Calculations
Materials 2022, 15(18), 6229; https://doi.org/10.3390/ma15186229 - 08 Sep 2022
Abstract
In situ X-ray crystallography powder diffraction studies on beta silicon carbide (3C-SiC) in the temperature range 25–800 °C at the maximum peak (111) are reported. At 25 °C, it was found that the lattice parameter is 4.596 Å, and coefficient thermal expansion (CTE) [...] Read more.
In situ X-ray crystallography powder diffraction studies on beta silicon carbide (3C-SiC) in the temperature range 25–800 °C at the maximum peak (111) are reported. At 25 °C, it was found that the lattice parameter is 4.596 Å, and coefficient thermal expansion (CTE) is 2.4 ×106/°C. The coefficient of thermal expansion along a-direction was established to follow a second order polynomial relationship with temperature (α11=1.423×1012T2+4.973×109T+2.269×106). CASTEP codes were utilized to calculate the phonon frequency of 3C-SiC at various pressures using density function theory. Using the Gruneisen formalism, the computational coefficient of thermal expansion was found to be 2.2 ×106/°C. The novelty of this work lies in the adoption of two-step thermal expansion determination for 3C-SiC using both experimental and computational techniques. Full article
(This article belongs to the Topic First-Principles Simulation—Nano-Theory)
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Article
First-Principles Calculations of the Structural, Electronic, Optical, and Mechanical Properties of 21 Pyrophosphate Crystals
Crystals 2022, 12(8), 1139; https://doi.org/10.3390/cryst12081139 - 12 Aug 2022
Abstract
Pyrophosphate crystals have a wide array of applications in industrial and biomedical fields. However, fundamental understanding of their electronic structure, optical, and mechanical properties is still scattered and incomplete. In the present research, we report a comprehensive theoretical investigation of 21 pyrophosphates A [...] Read more.
Pyrophosphate crystals have a wide array of applications in industrial and biomedical fields. However, fundamental understanding of their electronic structure, optical, and mechanical properties is still scattered and incomplete. In the present research, we report a comprehensive theoretical investigation of 21 pyrophosphates A2M (H2P2O7)2•2H2O with either triclinic or orthorhombic crystal structure. The molecule H2P2O7 is the dominant molecular unit, whereas A = (K, Rb, NH4, Tl), M = (Zn, Cu, Mg, Ni, Co, Mn), and H2O stand for the cation elements, transition metals, and the water molecules, respectively. The electronic structure, interatomic bonding, partial charge distribution, optical properties, and mechanical properties are investigated by first-principles calculations based on density functional theory (DFT). Most of these 21 crystals are theoretically investigated for the first time. The calculated results show a complex interplay between A, M, H2P2O7, and H2O, resulting in either metallic, half-metallic, or semi-conducting characteristics. The novel concept of total bond order density (TBOD) is used as a single quantum mechanical metric to characterize the internal cohesion of these crystals to correlate with the calculated properties, especially the mechanical properties. This work provides a large database for pyrophosphate crystals and a road map for potential applications of a wider variety of phosphates. Full article
(This article belongs to the Topic First-Principles Simulation—Nano-Theory)
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Article
Insight into Point Defects and Complex Defects in β-Mo2C and Carbide Evolution from First Principles
Materials 2022, 15(13), 4719; https://doi.org/10.3390/ma15134719 - 05 Jul 2022
Abstract
In this paper, first principles method was adopted to investigate the point defects, Vanadium-related defects and defect combinations (vacancy (V), substitutional (S) and/or interstitial (I)) in molybdenum β-Mo2C and explore the use of first principles calculation data in analysing the link [...] Read more.
In this paper, first principles method was adopted to investigate the point defects, Vanadium-related defects and defect combinations (vacancy (V), substitutional (S) and/or interstitial (I)) in molybdenum β-Mo2C and explore the use of first principles calculation data in analysing the link between different carbides and the effects of doping elements. Supercell models with different defect types were established and optimized, and the formation energy data of defects was developed. The structure evolution during the optimization process is analysed in detail to establish the main characteristics of changes and the relevant electronic properties. The data for different types of intrinsic defects and combined defects complexes was developed and key results is analysed. The results show that carbon vacancy (VC) is stable but does not inevitably exist in pure β-Mo2C. Interstitial site II is a very unstable position for any type of atoms (Mo, V and C), and analysis of the structure evolution shows that the atom always moves to the interface area near the interstitial site I between two layers. In particular, a C atom can expand the lattice structure when it exists between the layer interfaces. One type of the defects studied, the substitution of Mo with V (designated as ‘SV-Mo’), is the most stable defect among all single point defects. The data for defect complexes shows that the combination of multiple SV-Mo defects in the super cell being more stable than the combination of other defects (e.g., ‘VMo+IC’, ‘SV-Mo+VC’). The data with increasing SV-Mo in (Mo, V)2C system is developed, and typical data (e.g., formation energy) for Mo-rich carbides and V carbides are correlated and the potential of the data in analysing transition of different carbides is highlighted. The relevance of using first principles calculation data in the studying of V-doping and the complex carbides (V- and Mo-rich carbides) evolution in different materials systems and future focus of continuous work is also discussed. Full article
(This article belongs to the Topic First-Principles Simulation—Nano-Theory)
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Article
The Electronic Properties of g−ZnO Modulated by Organic Molecules Adsorption
Crystals 2022, 12(7), 882; https://doi.org/10.3390/cryst12070882 - 21 Jun 2022
Cited by 1
Abstract
Molecular doping is an excellent instrument to modify the electronic properties of two−dimensional materials. In our work, the structure and electronic properties of the adsorption systems of g−ZnO adsorbed by organic molecules (including Tetracyanoethylene (TCNE), Tetracyanoquinodimethane (TCNQ), and Tetrahydrofulvalene (TTF)) were investigated computationally [...] Read more.
Molecular doping is an excellent instrument to modify the electronic properties of two−dimensional materials. In our work, the structure and electronic properties of the adsorption systems of g−ZnO adsorbed by organic molecules (including Tetracyanoethylene (TCNE), Tetracyanoquinodimethane (TCNQ), and Tetrahydrofulvalene (TTF)) were investigated computationally using Density Functional Theory (DFT). The results showed that the TCNE and TCNQ, as electron receptors, doped the LUMO energy level above the valence band maximum (VBM) of the g−ZnO band structure, demonstrating effective p−type doping. The n−type doping of g−ZnO was obtained that the TTF molecules, as electron donors, doped the HOMO energy level below the conduction band minimum (CBM) of the band structure for g−ZnO. In addition, the TCNE, TCNQ, and TTF breathed additional holes or electrons into the monolayer g−ZnO, creating surface dipole moments between the g−ZnO and organic molecules, which caused work function to be adjustable, ranging from 3.871 eV to 5.260 eV. Our results prove that organic molecular doping was instrumental in improving the performance of g−ZnO−based nano−electronic devices, providing theoretical support for the fabrication of p−doping or n−doping nano−semiconductor components. The tunable range of field emission capability of g−ZnO−based electronic devices was also extended. Full article
(This article belongs to the Topic First-Principles Simulation—Nano-Theory)
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Article
The Role of Zr on Monoclinic and Orthorhombic HfxZryO2 Systems: A First-Principles Study
Materials 2022, 15(12), 4175; https://doi.org/10.3390/ma15124175 - 13 Jun 2022
Cited by 1
Abstract
HfO2 shows different polymorphs, including monoclinic and orthorhombic ones, that exhibit singular properties. Moreover, the character of HfO2 is also influenced by the Zr atoms as a doping agent. Here, an extensive study of the monoclinic P21/c and the [...] Read more.
HfO2 shows different polymorphs, including monoclinic and orthorhombic ones, that exhibit singular properties. Moreover, the character of HfO2 is also influenced by the Zr atoms as a doping agent. Here, an extensive study of the monoclinic P21/c and the orthorhombic Pca21 polymorphs of HfO2, Hf0.75Zr0.25O2, and Hf0.5Zr0.5O2 is reported. For all six systems, density functional theory (DFT) methods based on generalized gradient approximations (GGAs) were first used; then the GGA + U method was settled and calibrated to describe the electrical and optical properties of polymorphs and the responses to the oxygen vacancies. Zr had different effects in relation to the polymorph; moreover, the amount of Zr led to important differences in the optical properties of the Pca21 polymorph. Finally, oxygen vacancies were investigated, showing an important modulation of the properties of HfxZryO2 nanostructures. The combined GGA and GGA + U methods adopted in this work generate a reasonable prediction of the physicochemical properties of o- and m-HfxZryO2, identifying the effects of doping phenomena. Full article
(This article belongs to the Topic First-Principles Simulation—Nano-Theory)
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Article
Theoretical Prediction of Structures and Properties of 2,4,6-Trinitro-1,3,5-Triazine (TNTA) Green Energetic Materials from DFT and ReaxFF Molecular Modeling
Materials 2022, 15(11), 3873; https://doi.org/10.3390/ma15113873 - 29 May 2022
Abstract
Nitryl cyanide, O2NCN, as a new high-energy molecule, has not yet been successfully synthesized. It has prompted us to conduct a theoretical study of its possible space structures and properties. The RESP charges and the most stable spatial structures demonstrate that [...] Read more.
Nitryl cyanide, O2NCN, as a new high-energy molecule, has not yet been successfully synthesized. It has prompted us to conduct a theoretical study of its possible space structures and properties. The RESP charges and the most stable spatial structures demonstrate that crystal morphology is affected by both the main nonbonded interactions and the molecular arrangement. The crystal structure prediction indicated that there are seven structures, namely P1, P21, P212121, P21/c, Pna21, Pbca, and C2/c. The most stable space structure is likely to be Pna21 and the corresponding cell parameters are Z = 4, a = 8.69 Å, b = 9.07 Å, c = 9.65 Å, and α = β = γ = 90.0°. To further study the intermolecular interactions of TNTA, a series of theoretical analyses were employed, including Hirshfeld surface analysis and fingerprint plots. The pyrolysis mechanism and properties show that high temperatures can promote decomposition. The systematic search approach can be a new strategy to identify structures effectively and has the potential to provide systematic theoretical guidance for the synthesis of TNTA. Full article
(This article belongs to the Topic First-Principles Simulation—Nano-Theory)
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Article
First Principle Calculation of Accurate Electronic and Related Properties of Zinc Blende Indium Arsenide (zb-InAs)
Materials 2022, 15(10), 3690; https://doi.org/10.3390/ma15103690 - 21 May 2022
Cited by 1
Abstract
We carried out a density functional theory (DFT) study of the electronic and related properties of zinc blende indium arsenide (zb-InAs). These related properties include the total and partial densities of states and electron and hole effective masses. We utilized the local density [...] Read more.
We carried out a density functional theory (DFT) study of the electronic and related properties of zinc blende indium arsenide (zb-InAs). These related properties include the total and partial densities of states and electron and hole effective masses. We utilized the local density approximation (LDA) potential of Ceperley and Alder. Instead of the conventional practice of performing self-consistent calculations with a single basis set, albeit judiciously selected, we do several self-consistent calculations with successively augmented basis sets to search for and reach the ground state of the material. As such, our calculations strictly adhere to the conditions of validity of DFT and the results are fully supported by the theory, which explains the agreement between our findings and corresponding, experimental results. Indeed, unlike some 21 previous ab initio DFT calculations that reported zb-InAs band gaps that are negative or zero, we found the room temperature measured value of 0.360 eV. It is a clear achievement to reproduce not only the locations of the peaks in the valence band density of states, but also the measured values of the electron and hole effective masses. This agreement with experimental results underscores not only the correct description of the band gap, but also of the overall structure of the bands, including their curvatures in the vicinities of the conduction band minimum (CBM) and of the valence band maximum (VBM). Full article
(This article belongs to the Topic First-Principles Simulation—Nano-Theory)
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Article
Lattice Dynamics, Mechanical Properties, Electronic Structure and Magnetic Properties of Equiatomic Quaternary Heusler Alloys CrTiCoZ (Z = Al, Si) Using First Principles Calculations
Materials 2022, 15(9), 3128; https://doi.org/10.3390/ma15093128 - 26 Apr 2022
Abstract
First principles calculations are performed to investigate the thermodynamical stability, dynamical, mechanical, electronic and magnetic properties of CrTiCoZ (Z = Al/Si) novel quaternary Heusler alloys. A Y-type III atomic configuration is found to be the most stable structure for both compounds. The lattice [...] Read more.
First principles calculations are performed to investigate the thermodynamical stability, dynamical, mechanical, electronic and magnetic properties of CrTiCoZ (Z = Al/Si) novel quaternary Heusler alloys. A Y-type III atomic configuration is found to be the most stable structure for both compounds. The lattice constant values obtained using GGA-PBE approach are 5.9368 Å and 5.7853 Å for CrTiCoAl and CrTiCoSi, respectively. Using the value of elastic moduli for both the compounds, the computed Pugh’s ratio value is 2.5 and 2.7 for CrTiCoAl and CrTiCoSi, respectively, which is higher than 1.75, indicating both the compounds are ductile in nature. The melting temperatures of both compounds are as high as 2142 K and 2420 K for CrTiCoAl and CrTiCoSi, respectively. The electronic structure calculations, using the GGA-PBE approach, show a half metallic behavior of CrTiCoAl. The spin-down channel exhibits a direct band gap of 0.15 eV, whereas the spin-up channel is metallic, making CrTiCoAl a half metallic ferromagnet with 100% spin polarization and an appreciable magnetic moment of −2 μB. However, CrTiCoSi is found to be semi-metallic in the spin-down channel and metallic in the spin-up channel, which leads to a spin polarization of 99.7% with a non-integer magnetic moment of −0.99 μB. The Curie temperature of CrTiCoAl is well above the room temperature (385 K), whereas that of CrTiCoSi is below the room temperature (203 K). Thus, CrTiCoAl is found to be more promising than CrTiCoSi as a spin injector in spintronic devices. Full article
(This article belongs to the Topic First-Principles Simulation—Nano-Theory)
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Article
Periodicity of Superatomic Hybrid Orbitals in Substituted Superatoms and Superatomic-like [email protected]12 (X = Li~Kr) Clusters
Crystals 2022, 12(4), 543; https://doi.org/10.3390/cryst12040543 - 12 Apr 2022
Abstract
A superatom is a cluster composed of a specific number of atoms. We recently found that the superatom-like [email protected]12 (X = Li~Kr) clusters has the periodic energy levels of the specific orbitals 2S and 2P by means of the DV-Xα molecular orbital [...] Read more.
A superatom is a cluster composed of a specific number of atoms. We recently found that the superatom-like [email protected]12 (X = Li~Kr) clusters has the periodic energy levels of the specific orbitals 2S and 2P by means of the DV-Xα molecular orbital calculation method. This periodicity in energy levels has not been seen in 1D or 1F orbitals. We supposed that the periodicity of the energy levels of the 2S and 2P superatomic-like orbitals come from the same symmetry between atomic orbitals as the central atom X and the surrounding specific orbitals, according to the Jellium model. Both the s and p atomic orbitals of the central atom X in the superatom-like [email protected]12 have a large shielding effect, suggesting that the s and p atomic orbitals interact strongly with both 2S and 2P superatomic-like orbitals. The energy level periodicity has the potential to periodically change the number of electrons located in the 1D and 1F orbitals, which is related to magnetic properties and is expected to be useful for novel magnetic devices by periodically controlling the magnetism of superatoms. Full article
(This article belongs to the Topic First-Principles Simulation—Nano-Theory)
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Article
Effects of Mono-Vacancies of Oxygen and Manganese on the Properties of the MnO2/Graphene Heterostructure
Materials 2022, 15(8), 2731; https://doi.org/10.3390/ma15082731 - 08 Apr 2022
Cited by 2
Abstract
The effects of the monovacancies of oxygen (VO) and manganese (VMn) on the structural and electronic properties of the 1T–MnO2/graphene heterostructure are investigated, within the framework of density functional theory (DFT). We found that the values of [...] Read more.
The effects of the monovacancies of oxygen (VO) and manganese (VMn) on the structural and electronic properties of the 1T–MnO2/graphene heterostructure are investigated, within the framework of density functional theory (DFT). We found that the values of the formation energy for the heterostructure without and with vacancies of VO and VMn were −20.99 meV2 , −32.11meV2, and −20.81 meV2, respectively. The negative values of the formation energy indicate that the three heterostructures are energetically stable and that they could be grown in the experiment (exothermic processes). Additionally, it was found that the presence of monovacancies of VO and VMn in the heterostructure induce: (a) a slight decrease in the interlayer separation distance in the 1T–MnO2/graphene heterostructure of ~0.13% and ~1.41%, respectively, and (b) a contraction of the (Mn−O) bond length of the neighboring atoms of the VO and VMn monovacancies of ~2.34% and ~6.83%, respectively. Calculations of the Bader charge for the heterostructure without and with VO and VMn monovacancies show that these monovacancies induce significant changes in the charge of the first-neighbor atoms of the VO and VMn vacancies, generating chemically active sites (locales) that could favor the adsorption of external atoms and molecules. From the analysis of the density of state and the structure of the bands, we found that the graphene conserves the Dirac cone in the heterostructure with or without vacancies, while the 1T–MnO2 monolayer in the heterostructures without and with VO monovacancies exhibits half-metallic and magnetic behavior. These properties mainly come from the hybridization of the 3d–Mn and 2p–O states. In both cases, the heterostructure possesses a magnetic moment of 3.00 μβ/Mn. From this behavior, it can be inferred the heterostructures with and without VO monovacancies could be used in spintronics. Full article
(This article belongs to the Topic First-Principles Simulation—Nano-Theory)
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Article
First-Principles Study of Electronic Properties of Substitutionally Doped Monolayer SnP3
Materials 2022, 15(7), 2462; https://doi.org/10.3390/ma15072462 - 27 Mar 2022
Abstract
SnP3 has a great prospect in electronic and thermoelectric device applications due to its moderate band gap, high carrier mobility, absorption coefficients, and dynamical and chemical stability. Doping in two-dimensional semiconductors is likely to display various anomalous behaviors when compared to doping [...] Read more.
SnP3 has a great prospect in electronic and thermoelectric device applications due to its moderate band gap, high carrier mobility, absorption coefficients, and dynamical and chemical stability. Doping in two-dimensional semiconductors is likely to display various anomalous behaviors when compared to doping in bulk semiconductors due to the significant electron confinement effect. By introducing foreign atoms from group III to VI, we can successfully modify the electronic properties of two-dimensional SnP3. The interaction mechanism between the dopants and atoms nearby is also different from the type of doped atom. Both Sn7BP24 and Sn7NP24 systems are indirect bandgap semiconductors, while the Sn7AlP24, Sn7GaP24, Sn7PP24, and Sn7AsP24 systems are metallic due to the contribution of doped atoms intersecting the Fermi level. For all substitutionally doped 2D SnP3 systems considered here, all metallic systems are nonmagnetic states. In addition, monolayer Sn7XP24 and Sn8P23Y may have long-range and local magnetic moments, respectively, because of the degree of hybridization between the dopant and its adjacent atoms. The results complement theoretical knowledge and reveal prospective applications of SnP3-based electrical nanodevices for the future. Full article
(This article belongs to the Topic First-Principles Simulation—Nano-Theory)
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Article
Effective Approximation Method for Nanogratings-induced Near-Field Radiative Heat Transfer
Materials 2022, 15(3), 998; https://doi.org/10.3390/ma15030998 - 27 Jan 2022
Abstract
Nanoscale radiative thermal transport between a pair of metamaterial gratings is studied within this work. The effective medium theory (EMT), a traditional method to calculate the near-field radiative heat transfer (NFRHT) between nanograting structures, does not account for the surface pattern effects of [...] Read more.
Nanoscale radiative thermal transport between a pair of metamaterial gratings is studied within this work. The effective medium theory (EMT), a traditional method to calculate the near-field radiative heat transfer (NFRHT) between nanograting structures, does not account for the surface pattern effects of nanostructures. Here, we introduce the effective approximation NFRHT method that considers the effects of surface patterns on the NFRHT. Meanwhile, we calculate the heat flux between a pair of silica (SiO2) nanogratings with various separation distances, lateral displacements, and grating heights with respect to one another. Numerical calculations show that when compared with the EMT method, here the effective approximation method is more suitable for analyzing the NFRHT between a pair of relatively displaced nanogratings. Furthermore, it is demonstrated that compared with the result based on the EMT method, it is possible to realize an inverse heat flux trend with respect to the nanograting height between nanogratings without modifying the vacuum gap calculated by this effective approximation NFRHT method, which verifies that the NFRHT between the side faces of gratings greatly affects the NFRHT between a pair of nanogratings. By taking advantage of this effective approximation NFRHT method, the NFRHT in complex micro/nano-electromechanical devices can be accurately predicted and analyzed. Full article
(This article belongs to the Topic First-Principles Simulation—Nano-Theory)
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Article
First-Principles Density Functional Theory Study of Modified Germanene-Based Electrode Materials
Materials 2022, 15(1), 103; https://doi.org/10.3390/ma15010103 - 23 Dec 2021
Cited by 3
Abstract
Germanene, with a wrinkled atomic layer structure and high specific surface area, showed high potential as an electrode material for supercapacitors. According to the first-principles calculation based on Density Functional Theory, the quantum capacitance of germanene could be significantly improved by introducing doping/co-doping, [...] Read more.
Germanene, with a wrinkled atomic layer structure and high specific surface area, showed high potential as an electrode material for supercapacitors. According to the first-principles calculation based on Density Functional Theory, the quantum capacitance of germanene could be significantly improved by introducing doping/co-doping, vacancy defects and multilayered structures. The quantum capacitance obtained enhancement as a result of the generation of localized states near the Dirac point and/or the movement of the Fermi level induced by doping and/or defects. In addition, it was found that the quantum capacitance enhanced monotonically with the increase of the defect concentration. Full article
(This article belongs to the Topic First-Principles Simulation—Nano-Theory)
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Article
Phase Stability, Elastic Modulus and Elastic Anisotropy of X Doped (X = Zn, Zr and Ag) Al3Li: Insight from First-Principles Calculations
Crystals 2022, 12(1), 7; https://doi.org/10.3390/cryst12010007 - 21 Dec 2021
Abstract
In present work, the effects of alloying elements X (X = Zn, Zr and Ag) doping on the phase stability, elastic properties, anisotropy and Debye temperature of Al3Li were studied by the first-principles method. Results showed that pure and doped Al [...] Read more.
In present work, the effects of alloying elements X (X = Zn, Zr and Ag) doping on the phase stability, elastic properties, anisotropy and Debye temperature of Al3Li were studied by the first-principles method. Results showed that pure and doped Al3Li can exist and be stable at 0 K. Zn and Ag elements preferentially occupy the Al sites and Zr elements tend to occupy the Li sites. All the Cij obey the mechanical stability criteria, indicating the mechanical stability of these compounds. The overall anisotropy decreases in the following order: Al23Li8Ag > Al3Li > Al23Li8Zn > Al24Li7Zr, which shows that the addition of Zn and Zr has a positive effect on reducing the anisotropy of Al3Li. The shear anisotropic factors for Zn and Zr doped Al3Li are very close to one, meaning that elastic moduli do not strongly depend on different shear planes. For pure and doped Al3Li phase, the transverse sound velocities νt1 and νt2 among the three directions are smaller than the longitudinal sound velocity νl. Moreover, only the addition of Zn is beneficial to increasing the ΘD of Al3Li among the three elements. Full article
(This article belongs to the Topic First-Principles Simulation—Nano-Theory)
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Article
The Effects of Benzene on the Structure and Properties of Triethylamine Hydrochloride/Chloroaluminate
Crystals 2021, 11(12), 1532; https://doi.org/10.3390/cryst11121532 - 08 Dec 2021
Abstract
The effects of benzene (C6H6) on the radial distribution function, coordination number, spatial distribution function, physical and chemical properties such as density, viscosity, conductivity and transport properties of triethylamine hydrochloride /chloroaluminate ([Et3NH] Cl/AlCl3) ionic liquid [...] Read more.
The effects of benzene (C6H6) on the radial distribution function, coordination number, spatial distribution function, physical and chemical properties such as density, viscosity, conductivity and transport properties of triethylamine hydrochloride /chloroaluminate ([Et3NH] Cl/AlCl3) ionic liquid were studied by first principle and molecular dynamics simulation. The stable geometry and electronic properties of benzene and ionic liquids, as well as their optimized adsorption on Cu (111) surface were obtained. The density, viscosity and conductivity obtained agreed well with the experimental values. It is found that the adsorption of cations, anions and benzene on Cu (111) surface is physical adsorption, and the adsorption capacity is [Et3NH] > C6H6 > Al2Cl7. With the increase of benzene concentration, the density of the system decreases gradually, the interaction between cations and anions gradually weakens, resulting in the decrease of viscosity, the enhancement of diffusion and the increase of conductivity. Since the diffusion and adsorption capacity of benzene are greater than that of electroactive ion of Al2Cl7, benzene would be easier to adsorb on the protruding part of the electrode surface, so as to reduce the effective surface area of the cathode, slow down the reduction speed of Al2Cl7 on the cathode surface and increase the over-potential, so the grain refined deposition layers can be obtained in electrodeposition. Full article
(This article belongs to the Topic First-Principles Simulation—Nano-Theory)
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Article
Physical Properties Investigations of Ternary-Layered Carbides M2PbC (M = Ti, Zr and Hf): First-Principles Calculations
Crystals 2021, 11(12), 1445; https://doi.org/10.3390/cryst11121445 - 24 Nov 2021
Abstract
We investigated structure optimization, mechanical stability, electronic and bonding properties of the nanolaminate compounds Ti2PbC, Zr2PbC, and Hf2PbC using the first-principles calculations. These structures display nanolaminated edifices where MC layers are interleaved with Pb. The calculation of [...] Read more.
We investigated structure optimization, mechanical stability, electronic and bonding properties of the nanolaminate compounds Ti2PbC, Zr2PbC, and Hf2PbC using the first-principles calculations. These structures display nanolaminated edifices where MC layers are interleaved with Pb. The calculation of formation energies, elastic moduli and phonons reveal that all MAX phase systems are exothermic, and are intrinsically and dynamically stable at zero and under pressure. The mechanical and thermal properties are reported with fundamental insights. Results of bulk modulus and shear modulus show that the investigated compounds display a remarkable hardness. The elastic constants C11 and C33 rise more quickly with an increase in pressure than that of other elastic constants. Electronic and bonding properties are investigated through the calculation of electronic band structure, density of states, and charge densities. Full article
(This article belongs to the Topic First-Principles Simulation—Nano-Theory)
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Article
The Electronic Structural and Defect-Induced Absorption Properties of a Ca2B10O14F6 Crystal
Crystals 2021, 11(11), 1430; https://doi.org/10.3390/cryst11111430 - 22 Nov 2021
Abstract
Comprehensive ab initio electronic structure calculations were performed for a newly developed deep-ultraviolet (DUV) non-linear optical (NLO) crystal Ca2B10O14F6 (CBOF) using the first principle method. Fifteen point defects including interstitial, vacancy, antisite, Frenkel, and Schottky of [...] Read more.
Comprehensive ab initio electronic structure calculations were performed for a newly developed deep-ultraviolet (DUV) non-linear optical (NLO) crystal Ca2B10O14F6 (CBOF) using the first principle method. Fifteen point defects including interstitial, vacancy, antisite, Frenkel, and Schottky of Ca, O, F, and B atoms in CBOF were thoroughly investigated as well as their effects on the optical absorption properties. Their formation energies and the equilibrium concentrations were also calculated by ab initio total energy calculations. The growth morphology was quantitatively analyzed using the Hartman–Perdok approach. The formation energy of interstitial F (Fi) and antisite defect OF were calculated to be approximately 0.33 eV and 0.83 eV, suggesting that they might be the dominant defects in the CBOF material. The absorption centers might be induced by the O and F vacancies (VF, VO), interstitial B and O (Oi, Bi), and the antisite defect O substitute of F (OF), which might be responsible for lowering the damage threshold of CBOF. The ionic conductivity might be increased by the Ca vacancy (Vca), and, therefore, the laser-induced damage threshold decreases. Full article
(This article belongs to the Topic First-Principles Simulation—Nano-Theory)
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Article
An Investigation on Substitution of Ag Atoms for Al or Ti Atoms in the Ti2AlC MAX Phase Ceramic Based on First-Principles Calculations
Materials 2021, 14(22), 7068; https://doi.org/10.3390/ma14227068 - 21 Nov 2021
Cited by 1
Abstract
The present work introduced first-principles calculation to explore the substitution behavior of Ag atoms for Al or Ti atoms in the Ti2AlC MAX phase ceramic. The effect of Ag substitution on supercell parameter, bonding characteristic, and stability of the Ti2 [...] Read more.
The present work introduced first-principles calculation to explore the substitution behavior of Ag atoms for Al or Ti atoms in the Ti2AlC MAX phase ceramic. The effect of Ag substitution on supercell parameter, bonding characteristic, and stability of the Ti2AlC was investigated. The results show that for the substitution of Ag for Al, the Al-Ti bond was replaced by a weaker Ti-Ag bond, decreasing the stability of the Ti2AlC. However, the electrical conductivity of the Ti2AlC was enhanced after the substitution because of the contribution of Ag 4d orbital electrons toward the density of states (DOS) at the Fermi level coupled with the filling of Ti d orbital electrons. For the substitution of Ag for Ti, new bonds, such as Ag-Al bond, Ag-C bond, Al-Al bond, Ti-Ti anti-bond, and C-C anti-bond were generated in the Ti2AlC. The Ti-Ti anti-bond was strengthened as well as the number of C-C anti-bond was increased with increasing the substitution ratio of Ag for Ti. Similar to the substitution of Ag for Al, the stability of the Ti2AlC also decreased because the original Al-Ti bond became weaker as well as the Ti-Ti and C-C anti-bonds were generated during the substitution of Ag for Ti. Comparing with the loss of Ti d orbital electrons, Ag 4d orbits contributed more electrons to the DOS at the Fermi level, improving the electrical conductivity of the Ti2AlC after substitution. Based on the calculation, the substitution limit of Ag for Al or Ti was determined. At last, the substitution behavior of Ag for Al or Ti was compared to discriminate that Ag atoms would tend to preferentially substitute for Ti atoms in Ti2AlC. The current work provides a new perspective to understand intrinsic structural characteristic and lattice stability of the Ti2AlC MAX phase ceramic. Full article
(This article belongs to the Topic First-Principles Simulation—Nano-Theory)
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Article
Pressure Tuned Structural, Electronic and Elastic Properties of U3Si2C2: A First Principles Study
Crystals 2021, 11(11), 1420; https://doi.org/10.3390/cryst11111420 - 20 Nov 2021
Abstract
U3Si2C2 is expected to be a new nuclear fuel as a ternary compound of uranium, silicon and carbon. However, the relevant research on U3Si2C2 under accident conditions is rarely reported. Hence it is [...] Read more.
U3Si2C2 is expected to be a new nuclear fuel as a ternary compound of uranium, silicon and carbon. However, the relevant research on U3Si2C2 under accident conditions is rarely reported. Hence it is necessary to explore the service behavior of the potential U-Si-C ternary nuclear fuel in extreme environments. In this work, the structural characteristics, electronic behaviors and mechanical properties of U3Si2C2, such as stable crystalline structures, density of states, charge distributions, electron localization function, electronic thermal conductivity and elastic modulus under extreme high pressure are calculated by density functional theory. The calculation results show that the lattice volume sharply increases when the external stress reached 9.8 GPa. Ionic and metallic nature coexist as to the bonding characteristics of U3Si2C2, and the ionic takes the dominant position in bonding. The toughness of U3Si2C2 is predicted to be better compared to U3Si2. Our theoretical investigation may help with the application of U3Si2C2-based fuel and the design of ternary uranium fuels. Full article
(This article belongs to the Topic First-Principles Simulation—Nano-Theory)
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Article
Rational Design and Characterization of Symmetry-Breaking Organic Semiconductors in Polymer Solar Cells: A Theory Insight of the Asymmetric Advantage
Materials 2021, 14(21), 6723; https://doi.org/10.3390/ma14216723 - 08 Nov 2021
Cited by 10
Abstract
Asymmetric molecule strategy is considered an effective method to achieve high power conversion efficiency (PCE) of polymer solar cells (PSCs). In this paper, nine oligomers are designed by combining three new electron-deficient units (unitA)—n1, n2, and n3—and three electron-donating units (unit [...] Read more.
Asymmetric molecule strategy is considered an effective method to achieve high power conversion efficiency (PCE) of polymer solar cells (PSCs). In this paper, nine oligomers are designed by combining three new electron-deficient units (unitA)—n1, n2, and n3—and three electron-donating units (unitD)—D, E, and F—with their π-conjugation area extended. The relationships between symmetric/asymmetric molecule structure and the performance of the oligomers are investigated using the density functional theory (DFT) and time-dependent density functional theory (TD–DFT) calculations. The results indicate that asymmetry molecule PEn2 has the minimum dihedral angle in the angle between two planes of unitD and unitA among all the molecules, which exhibited the advantages of asymmetric structures in molecular stacking. The relationship of the values of ionization potentials (IP) and electron affinities (EA) along with the unitD/unitA π-extend are revealed. The calculated reorganization energy results also demonstrate that the asymmetric molecules PDn2 and PEn2 could better charge the extraction of the PSCs than other molecules for their lower reorganization energy of 0.180 eV and 0.181 eV, respectively. Full article
(This article belongs to the Topic First-Principles Simulation—Nano-Theory)
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Article
Employing Hybrid Lennard-Jones and Axilrod-Teller Potentials to Parametrize Force Fields for the Simulation of Materials’ Properties
Materials 2021, 14(21), 6352; https://doi.org/10.3390/ma14216352 - 24 Oct 2021
Abstract
The development of novel materials has challenges besides their synthesis. Materials such as novel MXenes are difficult to probe experimentally due to their reduced size and low stability under ambient conditions. Quantum mechanics and molecular dynamics simulations have been valuable options for material [...] Read more.
The development of novel materials has challenges besides their synthesis. Materials such as novel MXenes are difficult to probe experimentally due to their reduced size and low stability under ambient conditions. Quantum mechanics and molecular dynamics simulations have been valuable options for material properties determination. However, computational materials scientists may still have difficulty finding specific force field models for their simulations. Force fields are usually hard to parametrize, and their parameters’ determination is computationally expensive. We show the Lennard-Jones (2-body interactions) combined with the Axilrod-Teller (3-body interactions) parametrization process’ applicability for metals and new classes of materials (MXenes). Because this parametrization process is simple and computationally inexpensive, it allows users to predict materials’ behaviors under close-to-ambient conditions in molecular dynamics, independent of pre-existing potential files. Using the process described in this work, we have made the Ti2C parameters set available for the first time in a peer-reviewed work. Full article
(This article belongs to the Topic First-Principles Simulation—Nano-Theory)
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Article
Effects of the Addition of Co or Ni Atoms on Structure and Magnetism of FeB Amorphous Alloy: Ab Initio Molecular Dynamics Simulation
Materials 2021, 14(21), 6283; https://doi.org/10.3390/ma14216283 - 21 Oct 2021
Cited by 1
Abstract
The effects of the substitution of Fe by Co or Ni on both the structure and the magnetic properties of FeB amorphous alloy were investigated using first-principle molecular dynamics. The pair distribution function, Voronoi polyhedra, and density of states of Fe80−xTM [...] Read more.
The effects of the substitution of Fe by Co or Ni on both the structure and the magnetic properties of FeB amorphous alloy were investigated using first-principle molecular dynamics. The pair distribution function, Voronoi polyhedra, and density of states of Fe80−xTMxB20 (x = 0, 10, 20, 30, and 40 at.%, TM(Transition Metal): Co, Ni) amorphous alloys were calculated. The results show that with the increase in Co content, the saturation magnetization of Fe80−xCoxB20 (x = 0, 10, 20, 30, and 40 at.%) amorphous alloys initially increases and then decreases upon reaching the maximum at x = 10 at.%, while for Fe80−xNixB20 (x = 0, 10, 20, 30, and 40 at.%), the saturation magnetization decreases monotonously with the increase in Ni content. Accordingly, for the two kinds of amorphous alloys, the obtained simulation results on the variation trends of the saturation magnetization with the change in alloy composition are in good agreement with the experimental observation. Furthermore, the relative maximum magnetic moment was recorded for Fe70Co10B20 amorphous alloy, due to the induced increased magnetic moments of the Fe atoms surrounding the Co atom in the case of low Co dopant, as well as the increase in the exchange splitting energy caused by the enhancement of local atomic symmetry. Full article
(This article belongs to the Topic First-Principles Simulation—Nano-Theory)
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Article
Ab initio Investigation of Impurity Ferromagnetism in the Pd1−xFex Alloys: Concentration and Position Dependences
Crystals 2021, 11(10), 1257; https://doi.org/10.3390/cryst11101257 - 18 Oct 2021
Cited by 1
Abstract
We present the results of ab initio studies of the structural and magnetic properties of the Pd host matrix doped by Fe atoms at various concentrations. By means of the density functional theory, we deduce that iron impurities are able to initialize significant [...] Read more.
We present the results of ab initio studies of the structural and magnetic properties of the Pd host matrix doped by Fe atoms at various concentrations. By means of the density functional theory, we deduce that iron impurities are able to initialize significant magnetization of the Pd atoms, when the impurity concentration exceeds 3 at.%. We also demonstrate that the induced magnetization depends on impurity positions in the host matrix, in particular, there is a maximum of magnetization for a uniform distribution of the iron solute. Full article
(This article belongs to the Topic First-Principles Simulation—Nano-Theory)
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Article
First-Principles Simulation of Dielectric Function in Biomolecules
Materials 2021, 14(19), 5774; https://doi.org/10.3390/ma14195774 - 02 Oct 2021
Cited by 5
Abstract
The dielectric spectra of complex biomolecules reflect the molecular heterogeneity of the proteins and are particularly important for the calculations of electrostatic (Coulomb) and electrodynamic (van der Waals) interactions in protein physics. The dielectric response of the proteins can be decomposed into different [...] Read more.
The dielectric spectra of complex biomolecules reflect the molecular heterogeneity of the proteins and are particularly important for the calculations of electrostatic (Coulomb) and electrodynamic (van der Waals) interactions in protein physics. The dielectric response of the proteins can be decomposed into different components depending on the size, structure, composition, locality, and environment of the protein in general. We present a new robust simulation method anchored in rigorous ab initio quantum mechanical calculations of explicit atomistic models, without any indeterminate parameters to compute and gain insight into the dielectric spectra of small proteins under different conditions. We implement this methodology to a polypeptide RGD-4C (1FUV) in different environments, and the SD1 domain in the spike protein of SARS-COV-2. Two peaks at 5.2–5.7 eV and 14.4–15.2 eV in the dielectric absorption spectra are observed for 1FUV and SD1 in vacuum as well as in their solvated and salted models. Full article
(This article belongs to the Topic First-Principles Simulation—Nano-Theory)
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Article
Penetration of Chitosan into the Single Walled Armchair Carbon Nanotubes: Atomic Scale Insight
Crystals 2021, 11(10), 1174; https://doi.org/10.3390/cryst11101174 - 27 Sep 2021
Cited by 1
Abstract
(1) Background: Currently, nanomaterials have been broadly used in various applications including engineering, medicine and biology. One of the carbon allotropes such as carbon nanotubes (CNTs) implemented for fabrication of nanocomposite materials due to the hypersensitivity. The combined design of nanomaterial with chitosan [...] Read more.
(1) Background: Currently, nanomaterials have been broadly used in various applications including engineering, medicine and biology. One of the carbon allotropes such as carbon nanotubes (CNTs) implemented for fabrication of nanocomposite materials due to the hypersensitivity. The combined design of nanomaterial with chitosan (CS) and CNT expands the field of exploitation from biosensing and tissue engineering to water desalination. Therefore, the penetration of CS into CNT provides a valuable insight into the interactions between CS and CNT. (2) Methods: We performed molecular dynamics simulations, applying the umbrella sampling method, in order to calculate the potential mean force between CS and CNT. (3) Results: The estimated penetration free energies showed that CS is favorable to the penetration into CNT cavities. However, the penetration nature differs depending on the CNT’s architecture. (4) Conclusions: Our finding revealed the CS penetration process into CNT with nanoscale precision. The investigation results assist in a better understanding of the nanocomposite materials based on CS-CNT. Full article
(This article belongs to the Topic First-Principles Simulation—Nano-Theory)
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