Search Results (30)

The ONSET–OFFSET study was a multicentre study assessing the pharmacodynamic responses to ticagrelor and clopidogrel in aspirin-treated patients with chronic coronary syndromes. Recent concerns have been raised about the study methodology, including at the single United Kingdom (UK) site in Sheffield. Here, we report data generated at this site along with additional analyses. The UK site recruited 40 out of 123 of the study participants. Platelet P2Y₁₂ receptor inhibition was assessed using light transmission aggregometry and whole-blood methodologies. Samples were obtained during the onset and offset dosing periods. Percentage inhibition of platelet aggregation (%IPA) was calculated with (pre-specified) and without (post hoc) truncation of values [0, 100]. Study conduct was monitored by an external contract research organisation. The results from the UK site were concordant with the main study findings. %IPA at 2 h after ticagrelor loading: main study 88%, UK site 91% (truncated), UK site 91% (untruncated). %IPA correlated with other measures of P2Y₁₂ inhibition (VerifyNow: p < 0.0001; VASP phosphorylation assay: p < 0.0001). One patient treated with ticagrelor had >2 h delay in the onset of platelet inhibition associated with co-administration of metformin. The primary endpoint for the offset period was also similar to the main study findings. The UK site data confirm the more rapid onset and offset of inhibitory effects and greater mean levels of platelet inhibition with ticagrelor compared with clopidogrel, regardless of the mode of %IPA data analysis. Study conduct was rigorously monitored in order to demonstrate the integrity and validity of the results. Metformin may delay the onset of action of a ticagrelor loading dose. Full article

Zinc titanate (ZnTiO₃) is a chemically stable and non-toxic oxide perovskite whose photovoltaic potential remains largely unexplored due to its wide indirect bandgap. This study evaluates whether oxygen-vacancy (F-center) engineering can tailor its electronic structure and improve its suitability as a photovoltaic absorber. Density Functional Theory (DFT) calculations using VASP (PAW − GGA/PBE + U) were performed to evaluate structural stability, electronic properties, and electron affinity, while optical absorption was modeled through a combined Tauc–Gaussian approach. Device performance was assessed via SCAPS-1D simulations in an FTO/ZnO/ZnTiO₃/Spiro-OMeTAD architecture. Oxygen vacancies induce bandgap narrowing from ~2.96 eV to ~1.47 eV and generate Ti-3d-dominated donor-like and deep intragap states. The calculated electron affinity is ~3.77 eV. Simulated single-layer devices reach Voc ≈ 1.11 V, Jsc ≈ 8.27 mA·cm⁻², FF ≈ 83%, and a maximum efficiency of ~7.65%, primarily limited by moderate absorption strength and defect-assisted recombination. Multilayer configurations indicate that geometric optimization can significantly enhance projected efficiency, approaching 19.25% under idealized conditions. Although vacancy engineering extends visible-light absorption, the intrinsic indirect band-gap character constrains the ultimate photovoltaic performance of ZnTiO₃. Full article

The effect of LiPF₆ acidity, represented by LiPF₆·xHF adduct formation and its interaction with fluoride species, on the surface reactivity and stability of LiPF₆ was investigated using density functional theory (DFT) calculations performed with the Vienna Ab initio Simulation Package (VASP). The exchange–correlation energy was described using the Perdew–Burke–Ernzerhof (PBE) functional within the Generalized Gradient Approximation (GGA). Four distinct surface terminations of the (003) and (101) facets—F4–P2–Li, P2–F3–Li, Li2–F3–P, and F4–Li2–P were systematically examined. Surface and adsorption energies were evaluated together with key electronic descriptors, including the work function, dipole moment, electron localization function (ELF), electrostatic potential, band structure, and density of states, to elucidate the mechanisms governing adsorption and stability. The (101) facet exhibits a pronounced susceptibility to HF-induced solvation, driven by enhanced surface polarity, a low work function, and intermolecular H–F interactions at lithium-exposed terminations. In contrast, the thermodynamically dominant (003) facet shows greater resistance to HF interaction, with adsorption remaining predominantly molecular and progressing toward deliquescence only at elevated HF concentrations. Fluorine-rich and charge-balanced terminations on both facets display enhanced stability, characterized by high work functions, minimal ELF redistribution, and suppressed charge transfer. Full article

While graphene-based lubricants are well-studied, the tribological potential of emerging carbon–nitride and carbon–boron 2D materials remains largely unexplored. Herein, by using first-principles calculations implemented in the VASP code, we systematically explored the interlayer interactions and frictional properties of bilayer homojunctions and heterostructures composed of graphene, C₃N, and C₃B. The DFT-D3 dispersion correction was employed to accurately capture the interlayer van der Waals forces. The results reveal that C₃N/C₃N, C₃N/graphene (C₃N/Gra), and C₃B/graphene (C₃B/Gra) systems exhibit significantly lower friction coefficients compared to pristine bilayer graphene (Gra/Gra). Notably, the sliding potential barrier of the C₃N/Gra heterostructure is only ~0.45 meV/atom (approximately 1/10 that of the Gra/Gra system), manifesting exceptional superlubricity and considerable potential for superlubricant applications. The sliding potential barrier of the C₃B/C₃N heterostructure is slightly smaller than that of Gra/Gra. In contrast, the C₃B/C₃B homojunction exhibits high resistance to sliding; under normal loads of 1–4 nN, its potential barrier ranges from ~16 to ~115 meV/atom, which is consistently twice that of Gra/Gra. The observed frictional variations are attributed to sliding-induced interfacial charge redistribution. These findings provide fundamental insights into the tribological behavior of C₃N- and C₃B-based materials and establish a quantitative link between frictional properties and interfacial charge dynamics, offering a theoretical basis for the development of advanced graphene-derived lubricants. Full article

Until 2021, experimental data on polysulfide groups in feldspathoids were limited to the properties of the S₃^•− chromophore center and the S₂^•− luminescence center in sodalite-group minerals. Interpretation of some spectroscopic data on other S-bearing groups in feldspathoids remained ambiguous because of significant differences between calculated data for isolated polysulfide species and experimental data for polysulfide groups in liquid sulfur, solutions, and matrix-isolated species published in different literature sources. For this reason, configurations of stable and metastable structures and parameters of the absorption spectra in the ultraviolet, visible, and near-infrared (UV-Vis-NIR) region and in the ESR and Raman spectra of various structure modifications of polysulfide S_n²⁻ anions, S_n^•− radical anions, and S_n neutral molecules (n = 2–6) as well as HS⁻ in the sodalite cage of sapozhnikovite have been calculated in frames of the density functional theory using the VASP and ORCA software packages. Taking into account the obtained results of theoretical calculations, spectroscopic properties of extra-framework polysulfide groups in natural tectosilicates belonging to the cancrinite and sodalite groups are discussed. The obtained results made it possible to confirm and partially clarify the interpretation of the experimental spectroscopic data for S-containing feldspathoids obtained by the authors of this work over the past five years. Full article

Alongside the gradual progress of industrialization and the continuous development of human society, the problems of environmental pollution and energy crisis have become increasingly prominent. Semiconductor photocatalysis is a promising solution to these challenges. The photocatalytic reduction of CO₂ by TiO₂ to produce carbon monoxide and methane is a process which has been identified as a means of developing clean energy. In this paper, two-dimensional TiO₂ (2D-TiO₂) was synthesized via a one-step solvothermal method, and one-dimensional TiO₂ (1D-TiO₂) was obtained through a hydrothermal process. Their photocatalytic CO₂ reduction performances were systematically investigated. The results show that 2D-TiO₂ exhibits superior catalytic activity compared to 1D-TiO₂, which can be attributed to its lamellar structure, larger specific surface area, and improved hydrophilicity, providing more active sites and faster reaction kinetics. To further reveal the reaction mechanism, density functional theory (DFT) calculations were carried out using VASP with the GGA–PBE functional, PAW potentials, and a plane-wave cutoff energy of 520 eV. A 3 × 3 × 1 Monkhorst–Pack grid was used for Brillouin zone integration, and all possible adsorption configurations of CO₂*, COOH*, and CO* intermediates on the 2D-TiO₂ surface were evaluated. The results confirm that 2D-TiO₂ stabilizes key intermediates more effectively, thereby lowering the energy barrier and facilitating CO₂ reduction. These findings demonstrate that structural modulation of TiO₂ significantly influences its photocatalytic performance and highlight the great potential of 2D-TiO₂ for efficient CO₂ conversion and clean energy applications. Full article

A density functional theory-based study of UC₂ and Cr-doped UO₂ using the phono3py and VASP computational simulation packages is presented. Furthermore, the temperature-dependent thermal conductivities are compared to the traditional urania fuel. Doping of urania with Cr allows for improved fission gas retention, reducing the fission gas release and lowering the oxidation rate of UO₂. The thermal conductivity calculated using the random alloy method with one U atom replaced by Cr in a supercell (CrU₃₁O₆₄) shows a slight decrease; however, this may be compensated for by larger grain sizes in the presence of Cr. The reduction of thermal conductivity for the 0.61 wt.% Cr substation in urania is presented. Investigated here, the UC₂ metallic high-temperature fcc phase looks promising due to additional electronic contribution to conductivity. Furthermore, we found that the temperature-dependent phonon-assisted thermal conductivities for UC₂ and UO₂ are very similar. The elastic properties of UC₂ were also evaluated and compared with UO₂. The presented analysis provides information for further improvement of the design of nuclear fuels. Full article

This paper investigates the impact of sintering temperature on oxygen vacancy concentration and its subsequent effect on the microstructure and electrical properties of $B{i}_{4}T{i}_3{O}_{12}$ (BIT) ceramics. To further clarify these effects, VASP software was employed to simulate BIT ceramics with varying oxygen vacancy concentrations.The experimental results demonstrate that sintering temperature significantly influences the oxygen vacancy concentration. At the optimal sintering temperature of 1080 °C, the BIT ceramics exhibit a balanced microstructure with a grain size of 4.16 μm, the lowest measured oxygen vacancy concentration of 18.44%, and a piezoelectric coefficient ($d_{33}$) of 9.8 pC/N. Additionally, the dielectric loss ($tan\delta$) remains below 0.2 at 500 °C, indicating excellent thermal stability. VASP-based simulations reveal that increasing the oxygen vacancy concentration from 18.56% to 44.55% results in a significant collapse of the band gap (from 2.8 eV → 1.0 eV) and a transition in conductivity type from p-type to n-type. This shift induces a leakage current-dominated threshold effect, leading to a decrease in piezoelectric properties ($d_{33}$ reduced from 9.8 to 6.9 pC/N). Atomic-scale density of states (DOS) analyses indicate that the delocalization of $T{i}^{3+}$ and the weakening of Bi–O hybridization collectively induce lattice distortion and ferroelectric inconsistency. These changes are correlated with an increase in dielectric loss and a slight reduction in Curie temperature (from 620 °C → 618 °C). In conclusion, this study comprehensively elucidates the influence of oxygen vacancy concentration on the microstructure and electrical properties of BIT ceramics. The findings provide a theoretical foundation and practical insights for designing high-performance piezoelectric ceramics. Full article

CrystalShift is an open-source computational tool tailored for the analysis, transformation, and conversion of crystallographic data, with a particular emphasis on organic crystal structures. It offers a comprehensive suite of features valuable for the computational study of solids: format conversion, crystallographic basis transformation, atomic coordinate editing, and molecular layer analysis. These options are especially valuable for studying the mechanical properties of molecular crystals with potential applications in organic materials science. Written in the C programming language, CrystalShift offers computational efficiency and compatibility with widely used crystallographic formats such as CIF, POSCAR, and XYZ. It provides a command-line interface, enabling seamless integration into research workflows while addressing specific challenges in crystallography, such as handling non-standard file formats and robust error correction. CrystalShift may be applied for both in-depth study of particular crystal structure origins and the high-throughput conversion of crystallographic datasets prior to DFT calculations with periodic boundary conditions using VASP code. Full article

To meet the demands for functional layers in inverted flexible perovskite solar cells, high-performance formamidinium-based perovskite solar cells, and high-performance photodetectors in future applications, it is crucial to appropriately reduce the bandgap of third-generation wide-bandgap semiconductor materials. In this study, we first optimized doping sites through Ag-Cl and Ag-S configurations to establish stable substitution patterns, followed by density functional theory (DFT) calculations using the Generalized Gradient Approximation with the Perdew–Burke–Ernzerhof (GGA-PBE) functional, implemented in the Vienna Ab initio Simulation Package (VASP). A plane-wave basis set with a cutoff energy of 450 eV and a 3 × 4 × 3 Γ-centered k-mesh were adopted to investigate the effects of Mg-Cl, Mg-S, Zn-Cl, and Zn-S co-doping on the structural stability, electronic properties, and optical characteristics of β-Ga₂O₃. Based on structural symmetry, six doping sites were considered, with Ag-S/Cl systems revealing preferential occupation at octahedral Ga(1) sites through site formation energy analysis. The results demonstrate that Mg-Cl, Mg-S, Zn-Cl, and Zn-S co-doped systems exhibit thermodynamic stability. The bandgap of pristine β-Ga₂O₃ was calculated to be 2.08 eV. Notably, Zn-Cl co-doping achieves the lowest bandgap reduction to 1.81 eV. Importantly, all co-doping configurations, including Mg-Cl, Mg-S, Zn-Cl, and Zn-S, effectively reduce the bandgap of β-Ga₂O₃. Furthermore, the co-doped systems show enhanced visible light absorption (30% increase at 500 nm) and improved optical storage performance compared to the pristine material. Full article

Coal tar, a by-product of the pyrolysis of coal, is rich in aromatic compounds that have the potential to facilitate the synthesis of graphene, a high-quality carbon material, via low-temperature chemical vapor deposition (CVD). This approach offers a promising avenue for the cost-effective and large-scale industrial production of graphene while minimizing energy consumption. Nevertheless, there is a paucity of research focused on the low-temperature synthesis mechanisms of graphene derived from aromatic compounds in the context of graphene growth. To achieve high-quality graphene synthesis from coal tar and its aromatic constituents at reduced temperatures, a comprehensive investigation into the reaction pathways of these aromatic compounds is essential. In this study, we meticulously simulate the pyrolysis of benzene, a key aromatic component of coal tar, across various temperature settings utilizing reactive force field (ReaxFF) methodology. Furthermore, we apply density functional theory (DFT) calculations, executed through the Vienna Ab initio Simulation Package (VASP), to assess the dehydrogenation energy associated with the adsorption of benzene on vapor-deposited copper foils. Our molecular dynamics simulations, enhanced by a mixed force field approach, revealed that the dehydrogenated benzene ring (C₆ intermediate) acts as a critical precursor for graphene synthesis. This research significantly elucidates the reaction pathways of aromatic benzene in coal tar through molecular simulations conducted at different temperatures, both in the gas phase and on solid copper foil substrates. Full article

We performed first-principles density functional theory (DFT) calculations to numerically investigate the electronic band structures of penta-graphene (PG), a novel two-dimensional carbon material with a pentagonal lattice structure, and its chemically functionalized forms. Specifically, we studied hydrogenated PG (h-PG), fluorinated PG (f-PG), and chlorinated PG (Cl-PG). We used the generalized gradient approximation (GGA) and the hybrid Heyd–Scuseria–Ernzerhof (HSE06) exchange-correlation functional in the DFT-based software VASP to capture electronic properties accurately. Our results indicate that hydrogenation and fluorination increased the indirect bandgap of PG from 3.05 eV to 4.97 eV and 4.81 eV, respectively, thereby effectively transforming PG from a semiconductor to an insulator. In contrast, we found that chlorination closed the bandgap, thus indicating the metallic behavior of Cl-PG. These results highlight the feasibility of tuning the electronic properties of PG through functionalization, offering insight into designing new materials for nanoelectronic applications. Full article

Tetratoluene has the following three isomers: durene (DR), prehnitene (PR), and isodurene (IR). DR and PR often coexist during the separation of C10 heavy aromatics at different levels. They are both important organic chemical raw materials and their separation is the key to the high-efficiency industrial utilization of C10 heavy aromatics. In this paper, six metal–organic frameworks (MOFs), including ZU-61, MIL-101, UIO-66, UIO-66-NH₂, Mg-MOF-74, and MIL-53(Al), were used as the adsorbents of DR and PR. Their skeletons were structurally optimized using VASP software (latest v. 6.4.3). The adsorption capacity and isosteric heats of both pure components and mixtures (the molar ratio was 1:1) in gas were calculated using Grand Canonical Monte Carlo simulation from 10 kPa to 300 kPa at 298 K. The results indicated that all adsorption processes were physical. ZU-61, UIO-66, UIO-66-NH₂, and Mg-MOF-74 presented suitable capacity differences for DR and PR at 300 kPa. The selectivity values of these frameworks were all above 1.5. Thus, the four MOFs were prepared using the solvothermal method and characterized by SEM and XRD. Then, the competitive adsorption of DR and PR in liquid on the four MOFs was carried out as well. The results showed good agreement with the simulation in general, with a lower adsorption attained capacity due to the different phase states of both DR and PR. This study can guide the separation of tetratoluene isomers in C10 heavy aromatics. Full article

Semiconducting clathrates have attracted considerable interest in the field of thermoelectric materials. We report here a computational study on the crystal structure, the enthalpy of formation, and the physical properties of the following type-I clathrates: (a) experimentally studied Cs₈Sn₄₄ and hypothetical Cs₈Sn₄₆ and (b) hypothetical (NH₄)₈Sn_46−x (x = 0 or 2). The ab initio VASP calculations for the nominal stoichiometries include the geometry optimization of the initial structural models, enthalpies of formation, and the electronic and phonon density of states. Comparison of the chemical bonding of the structural models is performed via the electron localization function. The results show that the presence and distribution of defects in the Sn framework for both Cs₈Sn_46−x and (NH₄)₈Sn_46−x systems significantly alters the formation energy and its electrical properties, ranging from metallic to semiconducting behavior. In particular, one defect per six-membered Sn ring in a 3D spiro-network is the thermodynamically preferred configuration that results in the Cs₈Sn₄₄ and (NH₄)₈Sn₄₄ stoichiometries with narrow-band gap semiconducting behavior. Moreover, the rotation of the ammonium cation in the polyhedral cavities is an interesting feature that may promote the use of ammonium or other small molecular cations as guests in clathrates for thermoelectric applications; this is due to the decrease in the lattice thermal conductivity. Full article

We used the Vienna ab initio Simulation Package (VASP), X-ray photoelectron spectroscopy (XPS) and diffuse reflectance (DRS) to optimize anode material for a photoelectric catalytic system. After screening how the doping of TiO₂ by N and S affects its photoelectric properties, N-doped TiO₂ was selected to fabricate the photoelectron catalytic (PEC) system. TiO₂ nanotubes modified by N-doped TiO₂ nanocrystals and activated carbon were used as an anode and as a photocathode, respectively, to decompose carbamazepine in water samples from the constructed wetlands. The calculations showed that the N-TiO₂ NCs/TNTAs-AC/PTFE system had the highest content of •OH. The highest carbamazepine removal rate under the N-TiO₂ NCs/TNTAs-AC/PTFE composite presence was at pH = 8, and 69% of carbamazepine was removed within 180 min of the constructed wetland water treatment at pH = 7.8. The PEC system containing modified (with nano N-TiO₂) TiO₂ nanotubes as an anode and activated carbon as a photocathode can effectively decompose carbamazepine in the constructed wetlands. Full article