Crystals, Volume 14, Issue 6 (June 2024) – 71 articles

This work proposes the synthesis of strontium ferrite by two different methods: sol-gel (SG), using powdered coconut water (PCW) as a precursor, and laser floating zone (LFZ). The SG samples were after treated at temperatures of 700, 1000, and 1200 °C, while the samples obtained by LFZ were grown at pulling rates of 10, 50, and 100 mm/h. All samples studied were subjected to structural characterization techniques, as well as electrical (AC and DC) and magnetic characterization. Through X-ray diffraction, it was possible to observe that all the samples presented strontium ferrites, but none were single phase. The phases detected in XRD were confirmed by Raman spectroscopy. Scanning electron micrography allowed the observation of an increase in grain size with the temperature of SG samples and the reduction of the porosity with the decrease in growth rate for LFZ fibers. Through electrical analysis, it was observed that the most suitable samples for energy storage were the samples grown at 100 mm/h (${\epsilon }_r^{\prime }$ = 430,712; ${\epsilon }_r^{″}$ = 11,577; tan $\delta$ = 0.84; σ_ac = 0.0006 S/m, at 1 kHz). The remaining samples had high dielectric losses and can be applied in electromagnetic shielding. The SG 700 °C sample presented the highest magnetization (38.5 emu/g at T = 5 K). Full article

Silicon nitride (Si₃N₄) possesses excellent mechanical properties and high thermal conductivity, which is an important feature in many applications. However, achieving the theoretically high thermal conductivity of Si₃N₄ in practice is challenging. In this study, we adopted a first-principles calculation method to assess the effects of doping β-Si₃N₄ and γ-Si₃N₄ with carbon and oxygen atoms. Applying geometric structure optimization combined with calculation of the electronic phonon properties generated a stable doped structure. The results revealed that carbon and oxygen doping have little effect on the Si₃N₄ unit cell size, but that oxygen doping increases the unit cell volume. Energy band structure and state density calculation results showed that carbon doping reduces the nitride band gap width, whereas oxygen doping results in an n-type Si₃N₄ semiconductor. The findings from this study are significant in establishing a basis for targeted increase of the thermal conductivity of Si₃N₄. Full article

The effects of the ferrocenyl moiety to enhance the nucleophilicity of the carbonyl group, situated at its adjacent position, have been explored in a series of α-ferrocenyl ketocarboxylic acids. In the presence of trifluoroacetic anhydride, 3-ferrocenoylpropionic acid and 4-ferrocenoylbutyric acid gave 5-ferrocenyl-4-trifluoroacetyl-2(3H)-furanone and 6-ferrocenyl-5-trifluoroacetyl-3,4-dihydropyran-2-one, respectively. Under similar reaction conditions, 2-ferrocenylcarbonylbenzoic acid, a keto carboxylic acid without a β-hydrogen, gave a dimerized lactone, 3,3′-diferrocenyl-3,3′-diphthalide, possibly due to radical coupling. The nucleophilic attack of carbonyl oxygen, activated by the ferrocenyl moiety, on the carboxylic carbon is assumed to be the crucial mechanistic step in forming these lactones. When the carbonyl group was reduced to an alcohol to break its conjugation with the ferrocenyl moiety, saturated lactones were isolated after the acidic workup. These results indicate that the α-ferrocenyl carbinols readily undergo solvolysis under acidic conditions, giving ferrocenylcarbenium ions, which are attacked by the carboxy oxygen to give lactones. Full article

Double perovskite materials have gradually become widely studied due to their potential applications in solar cells and other optoelectronic devices. We take Cs₂NaFeCl₆ as an example to investigate the carrier mobility with respect to the acoustic phonon and the optical phonon scattering mechanisms. By considering the deformation potential, carrier effective mass, and bulk modulus, the longitudinal acoustic (LA) phonon-determined mobilities for electrons and holes in Cs₂NaFeCl₆ are found to be μ_e = 2886.08 cm² v⁻¹ s⁻¹ and μ_h = 39.09 cm² v⁻¹ s⁻¹, respectively. The optical scattering mechanism involves calculating the Fröhlich coupling constant, dielectric constant, and polaron mass to determine the multiple polar optical (PO) phonon-scattering-determined mobilities, resulting in μ_e = 279.25 cm² v⁻¹ s⁻¹ and μ_h = 21.29 cm² v⁻¹ s⁻¹, respectively. By combining both interactions, the total electron mobility and hole mobility are determined to be 254.61 cm² v⁻¹ s⁻¹ and 13.78 cm² v⁻¹ s⁻¹, respectively. The findings suggest that the polarization of both electrons and ions, small coupling constant, and bulk modulus in Cs₂NaFeCl₆’s lattice make PO scattering a significant contribution to carrier mobility in this specific double perovskite, highlighting the importance of considering this in enhancing the optoelectronic properties of Cs₂NaFeCl₆ and other double perovskites. Full article

The radiation-induced optical absorption at 1.5–5.5 eV (up to the beginning of fundamental absorption) has been analyzed in CVD diamond disks exposed to 231-MeV ¹³²Xe ions with four fluences from 10¹² to 3.8 × 10¹³ cm⁻². The 5 mm diameter samples (thickness 0.4 mm) were prepared by Diamond Materials, Freiburg (Germany); the average grain size at growth site was around 80 μm; and the range of xenon ions was R = 11.5 μm. The intensity of several bands grows with ion fluence, thus confirming the radiation-induced origin of the defects responsible for these bands. The recovery of radiation damage has been investigated via isochronal (stepwise) thermal annealing procedure up to 650 °C, while all spectra were measured at room temperature. Based on these spectra, the annealing kinetics of several defects, in particular carbon vacancies (GR1 centers with a broad band ~2 eV) and complementary C-interstitial-related defects (~4 eV), as well as impurity-related complex defects (narrow bands around 2.5 eV) have been constructed. The experimental kinetics have also been analyzed in terms of the diffusion-controlled bimolecular reactions. The migration energies of tentatively interstitial atoms (mobile components in recombination process) are obtained, and their dependence on the irradiation fluences is discussed. Full article

This article primarily presents cyclic voltammetry, Tafel polarization and ac. impedance spectroscopy electrochemical examinations of resorcinol (RC) electro-reactivity on the Pt(111) surface and its influence on the kinetics of UPD H (underpotentially deposited hydrogen) and the HER (hydrogen evolution reaction) in a 0.1 M NaOH supporting solution. The collected data provided evidence of the RC-ion’s surface adsorption and its further electroreduction in the presence of surface-adsorbed H radicals along with their primary beneficial role on the kinetics of the UPD H process. The above was elucidated through an evaluation of the associated charge-transfer resistance and capacitance parameters, and was carried out on the platinum (111) electrode plane, comparatively, for the RC-free and resorcinol-modified NaOH electrolyte. In addition, the recorded cathodic charge transients (obtained by injecting small amounts of RC-based 0.1 M NaOH solution to initially resorcinol-free electrolyte, carried out at the constant electrode potential characteristic to the UPD H potential zone) provided evidence that the RC species undergoes electrocatalytic reduction through the involvement of the Pt(111)-chemisorbed hydrogen radicals. Full article

A change in the growth mode from Stranski–Krastanov one, which is characteristic of MOCVD grown GaN, to the laterally grown BGaN in the Volmer–Weber growth mode is described. This change in growth is evidenced by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images of BGaN grown on GaN at high temperatures. It is postulated on the basis of SIMS and XRD results that this change in growth is initiated by the transfer of boron atoms from gallium substitutional to interstitial. The proposed mechanism for the observed growth change is related to the generation of nitrogen interstitials and subsequent reactions with boron interstitials, which result in the formation of a BN layer at the growth front. The observed large change in the growth mode is due to a lattice mismatch between the grown BGaN and the atomic layer of BN and stays behind the change to the Volmer–Weber growth mode. The consequence of the Volmer–Weber growth mode is the textural layer of BGaN. The textural character of this material is associated with large voids between grown BGaN “plates”. These large voids are responsible for the termination of threading dislocations propagating in the c-direction. It is also postulated that the blocked threading dislocations from the GaN underlayer and laterally grown BGaN layers along the a-directions are responsible for the decrease in defect concentration within these layers. Full article

In this manuscript, for the first time, the exploration of the microstructural, ferroelectric, piezoelectric, and dielectric performances are measured for Sm-ion-influenced pseudo-cubic, morphotropic phase boundary (MPB) regional 0.62BiFeO₃−0.38SrTiO₃:xwt%Sm₂O₃ (BFST:xSm) ceramics with x = 0–0.25. All the compositions maintained their pseudo-cubic MPB structural stability. The composition of BFST:0.15Sm ceramics exhibited an excellent remnant polarization (P_r) of ~52.11 μC/cm², an enhanced d₃₃ of 101 pC/N, and the highest relative dielectric constant (ɛ_r) of ~1152, which are much improved as compared to that of pure BFST ceramics. BFST:0.15Sm ceramics demonstrated a Curie temperature (T_C) of 378 °C. Moreover, the composition exhibited high thermal stability for d₃₃ 72 pC/N (only a 28% decrease), even at a high temperature of 300 °C. Such outstanding outcomes make BFST:0.15Sm ceramics an ideal applicant for high-temperature piezoelectric applications. Full article

We report the absorption and photoluminescence spectra of GaSe single crystals in the near-edge region. The temperatures explored the range from 17 to 300 K. Specifically, at a temperature of 17 K, the photoluminescence spectrum reveals an interesting phenomenon: the Wannier-Mott exciton separates into two states. These states are a triplet state with an energy of 2.103 eV and a singlet state with an energy of 2.109 eV. The energy difference between these two states is 6 meV. Furthermore, the bound exciton (BX) can be localized at an energy of 2.093 eV. It is worth noting that its phonon replicas (BX-nLO) can be clearly distinguished up to the fourth order. Interestingly, the energy gaps between these replicas exhibit a consistent spacing of 7 ± 0.5 meV. This intriguing finding suggests a high-quality crystalline structure as well as a strong coupling between the phonon and BX-nLO. Additionally, at low temperatures, both the ground state (n = 1) at 2.11 eV and the excited state (n = 2) at 2.127 eV of free excitons can be observed. Full article

The structural, elastic, and electronic properties of orthorhombic Cd₂SiO₄ and Hg₂GeO₄ were examined under varying pressure conditions using first-principles calculations based on density functional theory employing the Projector Augmented Wave method. The obtained cell parameters at 0 GPa were found to align well with existing experimental data. We delved into the pressure dependence of normalized lattice parameters and elastic constants. In Cd₂SiO₄, all lattice constants decreased as pressure increased, whereas, in Hg₂GeO₄, parameters a and b decreased while parameter c increased under pressure. Employing the Hill average method, we calculated the elastic moduli and Poisson’s ratio up to 10 GPa, noting an increase with pressure. Evaluation of ductility/brittleness under pressure indicated both compounds remained ductile throughout. We also estimated elastic anisotropy and Debye temperature under varying pressures. Cd₂SiO₄ and Hg₂GeO₄ were identified as indirect band gap insulators, with estimated band gaps of 3.34 eV and 2.09 eV, respectively. Interestingly, Cd₂SiO₄ exhibited a significant increase in band gap with increasing pressure, whereas the band gap of Hg₂GeO₄ decreased under pressure, revealing distinct structural and electronic responses despite their similar structures. Full article

The study of the properties of ferroelectric materials against irradiation has a long history. However, anti−irradiation research on the ferroelectric domain has not been carried out. In this paper, the irradiation of switched domain structure is innovatively proposed. The switched domain of 700 nm lithium niobate (LiNbO₃, LN) thin film remains stable after gamma irradiation from 1 krad to 10 Mrad, which was prepared by piezoresponse force microscopy (PFM). In addition, the changing law of domain wall resistivity is explored through different sample voltages, and it is verified that the irradiated domain wall conductivity is still larger than the domain. This domain wall current (DWC) property can be applied to storage, logic, sensing, and other devices. Based on these, a ferroelectric domain irradiation resistance model is established, which explains the reason at an atomic level. The results open a possibility for exploiting ferroelectric materials as the foundation in the application of space and nuclear fields. Full article

For the first time, the Z₁ and Z₂ defects with closely spaced energy levels having negative-U properties are revealed in high-purity semi-insulating (HPSI) 4H-SiC using Laplace-transform photoinduced transient spectroscopy (LPITS). In this material, after switching off the optical trap-filling pulse, either the one-electron or the two-electron thermally stimulated emission from these defects is observed at temperatures 300–400 K. It is found that the former corresponds to the Z₁^0/+ and Z₂^0/+ transitions with the activation energies of 514 and 432 meV, respectively, and the latter is associated with the Z₁^−/+ and Z₂^−/+ transitions with the activation energies of 592 meV and 650 meV, respectively. The Z₁ and Z₂ defect concentrations are found to increase from 2.1 × 10¹³ to 2.2 × 10¹⁴ cm⁻³ and from 1.2 × 10¹³ to 2.7 × 10¹⁴ cm⁻³, respectively, after the heat treatment of HPSI 4H-SiC samples at 1400 °C for 3 h in Ar ambience. Using the electrical trap-filling pulse, only the thermal two-electron emission from each defect was observed in the epitaxial 4H-SiC through Laplace-transform deep level transient spectroscopy (LDLTS). The activation energies for this process from the Z₁ and Z₂ defects are 587 and 645 meV, respectively, and the defect concentrations are found to be 6.03 × 10¹¹ and 2.64 × 10¹² cm⁻³, respectively. It is postulated that the Z₁ and Z₂ defects are the nearest-neighbor divacancies involving the carbon and silicon vacancies located at mixed, hexagonal (h), and quasi-cubic (k) lattice sites. Full article

In directional forming processes, such as rolling and extrusion, the grains can develop preferred crystal orientations. These preferred orientations—the texture—are the main cause for material anisotropy. This anisotropy leads to phenomena such as earing, which occur during further forming processes, e.g., during the deep drawing of sheet metal. Considering anisotropic properties in numerical simulations allows us to investigate the effects of texture-dependent defects in forming processes and the development of possible solutions. Purely phenomenological models for modeling anisotropy work by fitting material parameters or applying measured anisotropy properties to all elements of the part, which remain constant over the duration of the simulation. In contrast, crystal plasticity methods, such as the visco-plastic self-consistent (VPSC) model, provide a deeper insight into the development of the material microstructure. By experimentally measuring the initial texture and using it as an initial condition for the simulations, it is possible to predict the evolution of the microstructure and the resulting effect on the mechanical properties during forming operations. The results of the simulations with the VPSC model show a good agreement with corresponding compression tests and the earing phenomenon, which is typical for cup deep drawing. Full article

We present an analysis of α-helix folding in the coarse-grained coordinate of number of formed helical hydrogen bonds (NHBs) for four alanine peptides (ALA)n, with n = 5, 8, 15, and 21 residues. Starting with multi-microsecond all-atom molecular dynamics trajectories in aqueous solution, we represent the system dynamics in a space of between four (for ALA5) and twenty (for ALA21) hydrogen-bonding microstates. In all cases, transitions changing the hydrogen bond count by 1–2 dominate and the coil formation, NHB 1 → 0, is the fastest process. The calculation of global maximum weight paths shows that, when analyzed at a sufficiently long lag time, folding in the NHB coordinate is consecutive, with direct folding, 0 → 3, for ALA5 and bottlenecks at transitions 4 → 6 for ALA8, 0 → 5 for ALA15, and 0 → 9 for ALA21. Further coarse-graining to 2–4 dimensions was performed with the optimal dimensionality reduction method, allowing the identification of crucial folding intermediates and time scales of their formation in ALA8, ALA15, and ALA21. The detailed analysis of hydrogen bonding patterns revealed that folding is initiated preferentially at both peptide termini. The kinetic model was also used to estimate diffusion and friction coefficients for helix propagation. The description of the helix formation process in the hydrogen bonding coordinate NHB was in good general agreement with the experimental data and qualitatively similar to previous kinetic models of higher dimensions based on structural clustering. Use of the low-dimensional hydrogen bonding picture thus provides a different, complementary way of describing the complex and fascinating mechanism of helix formation. Full article

Austenitic stainless steels used in structural applications suffer from stress corrosion cracking due to residual stresses during welding. Much research is being conducted to prevent the stress corrosion cracking of austenitic steels by inducing compressive residual stresses. One method is ultrasonic shot peening (USP), which is used to apply compressive stress by modifying the mechanical properties of the material’s surface. In this study, 304L stainless steel was butt-welded by gas tungsten arc welding (GTAW) and subsequently subjected to compressive residual stress to a depth of 1 mm from the surface by a USP treatment. The influence of USP on microstructural changes in the base metal, the HAZ and weldment, and the corrosion properties was analyzed. A microstructural analysis was conducted using SEM-EDS, XRD, and EBSD methods alongside residual stress measurements. The surface and cross-sectional corrosion behavior was evaluated and analyzed using a potentiodynamic polarization test, electrochemical impedance spectroscopy (EIS) measurements, a double-loop electrochemical potentiokinetic reactivation (DL-EPR) test, and an ASTM A262 Pr. C test. The surface was deformed and roughened by the USP. The deformed areas formed crevices, and the inside of the crevices contained some cracks. The crevices and internal cracks caused pitting, which reduced the resistance of the passivation film. The cross-section was subjected to compressive residual stress to a depth of 1 mm from the surface, and the outermost area of the cross-section had fine grain refinement, forming a solid passivation film that improved the corrosion resistance. Full article

Upon exposure to irradiation, trans-cinnamic acid can dimerize, producing truxinic and truxillic acids, regioisomers distinguished by the relative arrangement of acid and phenyl groups on the formed cyclobutane ring. Solid-state dimerization, governed by Schmidt’s specified conditions, hinges on the initial molecular setup. This study endeavors to manipulate the reaction’s outcome in the solid state. To achieve this, the target molecule was paired with metals (Ag, Cu) to modify molecular orientation in the solid. Investigated derivatives included para-hydroxy-trans-cinnamic acid, ortho-methoxy-trans-cinnamic acid, ortho-ethoxy-trans-cinnamic acid, and ortho-chloro-trans-cinnamic acid. Despite easy synthesis of all complexes, only the complex between Ag and ortho-chloro-trans-cinnamic acid exhibits photoreactivity, mirroring the outcome of the metal-free derivative. Thus, while this approach has the potential to alter the photobehavior of cinnamic acid derivatives, obtaining the desired structure will require extensive screening to identify an appropriate metal complex. Full article

One of the major sources of catastrophic failures and deterioration of the mechanical properties of metals, such as ductility, toughness, and strength, in various engineering components during application is hydrogen embrittlement (HE). It occurs as a result of the adsorption, diffusion, and interaction of hydrogen with various metal defects like dislocations, voids, grain boundaries, and oxide/matrix interfaces due to its small atomic size. Over the years, extensive effort has been dedicated to understanding hydrogen embrittlement sources, effects, and mechanisms. This study aimed at assessing the tensile properties, toughness, ductility, and susceptibility to hydrogen embrittlement of cold-finished mild steel. Steel coupons were subjected to electrochemical hydrogen charging in a carefully chosen alkaline solution over a particular time and at various charging current densities. Tensile property tests were conducted immediately after the charging process, and the results were compared with those of uncharged steel. The findings revealed a clear drop in toughness and ductility with increasing hydrogen content. Fracture surfaces were examined to determine the failure mechanisms. This evaluation has enabled the prediction of steel’s ability to withstand environments with elevated hydrogen concentrations during practical applications. Full article

This study evaluates the feasibility of producing high-strength low-alloy (HSLA) steel using advanced wire-fed laser additive manufacturing (LAM-W) and wire arc additive manufacturing (WAAM) technologies. Optimized parameters were independently developed for each heat source, utilizing a self-designed HSLA steel wire as the feedstock. Microstructural features and mechanical properties of the fabricated steels were characterized and compared, taking into account differences in heat input and cooling rates. LAM-W samples exhibited a finer columnar grain microstructure, while both LAM-W- and WAAM-produced steels predominantly showed lower bainite and granular bainite microstructures. LAM-W demonstrated higher strength and hardness, lower ductility, and comparable low-temperature toughness compared to WAAM. Both processes demonstrated an excellent balance between strength and ductility, with absorbed energy exceeding 100 J at −40 °C. The study confirms the feasibility of producing high-strength and tough HSLA steel parts using LAM-W and WAAM technologies, and compares the advantages and disadvantages of each method. These findings assist in selecting the most suitable wire-fed AM process for HSLA steel fabrication at high deposition rates. Full article

The problem of large stockpiles of red mud needs to be solved, and the use of red mud to prepare inorganic fibers is a new way of applying red mud on a large scale. The role of CaO/Al₂O₃ in the melting point and melt structure of red mud was investigated by molecular dynamics simulations and thermodynamic calculations. Liquid phase line temperatures for different CaO/Al₂O₃ systems were calculated using the Factsage program. The radial distribution function and the type of oxygen bonding were used to characterize the effect of different CaO/Al₂O₃ on the structure of the red mud melt. The melting point of MgAl₂O₄ is lower than that of CaTiO₃ due to the fact that the type of oxygen bonding in MgAl₂O₄ is predominantly bridging oxygen bonds. When the red mud system has a low SiO₂ content and CaO/Al₂O₃ is between 0.3 and 3.9, the melting point temperature increases significantly, which is not conducive to the fibrillation of the red mud melt. Full article

The mechanical performance of pure copper can be significantly strengthened by adding graphene without greatly sacrificing its electrical and thermal conductivity. However, it is difficult to observe the deformation behavior of Cu/graphene composites efficiently and optically using experiments due to the extremely small graphene size. Herein, Cu/graphene composites with different graphene positions and layers were built to investigate the effect of these factors on the mechanical performance of the composites and the deformation mechanisms using molecular dynamics simulations. The results showed that the maximum indentation force and hardness of the composites decreased significantly with an increase in the distance from graphene to the indentation surface. Graphene strengthened the mechanical properties of Cu/graphene composites by hindering the slip of dislocations. As the graphene layers increased, the strengthening effect became more pronounced. With more graphene layers, dislocations within the Cu matrix were required to overcome higher stress to be released towards the surface; thus, they had to store enough energy to allow more crystalline surfaces to slip, resulting in more dislocations being generated. Full article

The demand for sustainable and cost-effective materials for photovoltaic technology has led to an increasing interest in Cu₃BiS₃ thin films as potential absorber layers. This review provides a comprehensive overview of the main physical properties, synthesis methods, and theoretical studies of Cu₃BiS₃ thin films for photovoltaic applications. The high optical absorption coefficient and band gap energy around the optimal 1.4 eV make Cu₃BiS₃ orthorhombic Wittichenite-phase a promising viable alternative to conventional thin film absorber materials such as CIGS, CZTS, and CdTe. Several synthesis techniques, including sputtering, thermal evaporation, spin coating, chemical bath deposition, and spray deposition, are discussed, highlighting their impact on film quality and photovoltaic performance. Density Functional Theory studies offer insights into the electronic structure and optical properties of Cu₃BiS₃, aiding in the understanding of its potential for photovoltaic applications. Additionally, theoretical modeling of Cu3BiS3-based photovoltaic cells suggests promising efficiencies, although experimental challenges remain to be addressed. Overall, this review underscores the potential of CBS thin films as sustainable and cost-effective materials for future PV technology while also outlining the ongoing research efforts and remaining challenges in this field. Full article

First, a recently developed eigenfunction expansion technique, based in part on the separation of the thickness variable and partly utilizing a modified Frobenius-type series expansion technique in conjunction with the Eshelby–Stroh formalism, is employed to derive three-dimensional singular stress fields in the vicinity of the front of an interfacial crack weakening an infinite bicrystalline superlattice plate, made of orthorhombic (cubic, hexagonal, and tetragonal serving as special cases) phases of finite thickness and subjected to the far-field extension/bending, in-plane shear/twisting, and anti-plane shear loadings, distributed through the thickness. Crack-face boundary and interface contact conditions as well as those that are prescribed on the top and bottom surfaces of the bicrystalline superlattice plate are exactly satisfied. It also extends a recently developed concept of the lattice crack deflection (LCD) barrier to a superlattice, christened superlattice crack deflection (SCD) energy barrier for studying interfacial crack path instability, which can explain crack deflection from a difficult interface to an easier neighboring cleavage system. Additionally, the relationships of the nature (easy/easy, easy/difficult, or difficult/difficult) interfacial cleavage systems based on the present solutions with the structural chemistry aspects of the component phases (such as orthorhombic, tetragonal, hexagonal, as well as FCC (face-centered cubic) transition metals and perovskites) of the superlattice are also investigated. Finally, results pertaining to the through-thickness variations in mode I/II/III stress intensity factors and energy release rates for symmetric hyperbolic sine-distributed loads and their skew-symmetric counterparts that also satisfy the boundary conditions on the top and bottom surfaces of the bicrystalline superlattice plate under investigation also form an important part of the present investigation. Full article

In our study, we utilize molecular dynamics simulations, specifically through the Reactive Empirical Bond Order, to unravel atomic-scale dynamics in graphite, an essential component in many advanced technologies, under varying irradiation scenarios. We shed light on the behavior of graphite when exposed to Primary Knock-on Atom (PKA) energies of 10, 20, 40, and 80 keV. The findings highlight the radiation vulnerability of graphite, especially when influenced by hydride inclusion. Both pristine graphite and its hydride variant exhibited an increase in Frenkel pairs (FPs) with escalating PKA energies. Notably, carbon PKAs manifested significant FP effects, whereas hydrogen PKAs influenced defect formation through variable diffusivity. In tested radiation scenarios, particularly in Mode C and the R1 region, cascade patterns identified distinct defect forms of diamond-like and elongated-diamond-like shapes, distinct from the typical PKA collision clusters. Furthermore, our cascade findings emphasize the formation of three-coordinated graphite rings, particularly as PKA energies increase. The graphite population statistics reveal a decline in threefold-coordinated atoms and an increase in other types of defects, with 7-carbon atom rings being the most common. Our research highlights the significance of understanding three-coordinated graphite rings, especially as PKA energies rise. Graphite population statistics reveal a decline in threefold-coordinated atoms and a rise in other defects. Notably, 7-carbon atom rings are the most common. From a clustering perspective, self-interstitial atom (SIA) clusters predominated in pristine graphite, while this trend balanced in the hydride variant. Our research highlights the importance of understanding atomic behaviors in graphite under several radiation scenarios. This knowledge is needed for advancing reliable and efficient technological applications, particularly in the field of nuclear technology. Our research underscores the need to understand atomic behaviors in graphite under radiation, paving the way for detailed study on reliable efficient technological applications. Full article

Metamaterials are artificial materials with properties depending mainly on their designed structures instead of their materials. Pentamode metamaterials are one type of metamaterial. They have solid structures with fluid-like properties, which can only withstand compressive stresses, not shear stresses. Two-dimensional pentamode metamaterials are easier to manufacture than three-dimensional models, so they have received wide attention. In this review, the properties, manufacturing, and applications of two-dimensional pentamode metamaterials will be discussed. Their water-like properties are their most important properties, and their velocities and anisotropy can be designed. They can be processed by wire-cut electrical discharge machining, waterjet cutting, and additive manufacturing techniques. They have a broad application prospect in acoustic fields such as acoustic stealth cloaks, acoustic waveguides, flat acoustic focusing lenses, pentamode acoustic meta-surfaces, etc. Full article