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The energy band gaps (EgL, EgΓ and EgX) and electronic band structure in the pentanary AlxIn1-xPySbzAs1-y-z semiconducting alloy are determined. Additionally, the Fröhlich coupling parameter, the phonon frequencies (ωLO, ωTO), transverse effective charge (eT*), high-frequency dielectric constant (ε∞), static dielectric constant (ε0) and refractive index (n) are calculated. A combination of the virtual crystal approximation and the empirical pseudopotential approach is used in our study. The calculations are done at room temperature and normal pressure. The studied properties for the new alloy under investigation lattice-matched to the InP substrate give a good agreement with the experiment. It is discovered that materials with lower coupling constants are advantageous for a parametric interaction to be cost-effective. It is expected that this paper's findings will apply to a wide range of industrial applications. [ABSTRACT FROM AUTHOR]

In this work, the sound velocity and some of the mechanical, optical and optical phonon frequencies of the semiconductor β-GaN have been studied. The proposed temperature dependency of the pseudopotential form factors was used together with the empirical pseudopotential technique (EPM). The precise form factors for each temperature are computed using the suggested model. Calculations have been done to determine the temperature-dependent values of the energy gaps, sound velocity, refractive index, elastic constants, mechanical moduli, phonon frequencies and dielectric constants. The findings and the published and experimental data in the literature are in good agreement. These findings can be used as a guide for physical parameter values that are difficult to quantify experimentally. [ABSTRACT FROM AUTHOR]

First-principle calculations are carried out to explore magnesium composition-dependent structural and optoelectronic features of wurtzite MgxZn1−xSe ternary alloys. Analyses show a nearly linear enhancement in lattice constants (a0, c0) but a reasonably nonlinear reduction in bulk modulus (B0) with increasing Mg composition. Successive incorporation of Mg atom(s) in place of Zn in the w-ZnSe crystal results in three direct-band gap (Γ–Γ) semiconductor ternary alloys. The fundamental band gap shows fairly nonlinear enhancement with increasing Mg composition. Each of the considered wurtzite specimens is optically anisotropic. The computed components of the refractive index give uniaxial birefringence. Peaks in the dielectric function spectrum of all the specimens in the ultraviolet (UV) region are contributed exclusively or collectively by Se-4p to Mg-4s, 3p and Zn-5s, 4p electronic excitations. With the enhancement in the fundamental band gap, static optical constants ε1(0), n(0) and R(0) of the specimens reduce, while critical point energy in their ε2(ω), k(ω), σ(ω), α(ω) spectra enhances. [ABSTRACT FROM AUTHOR]

Based on the first-principles calculations, we have systematically investigated the structural stability, mechanical, electronic and bonding properties of TMB2 (TM = Y, Sc, Ti) under pressure for the first time. The results show that these TMB2 (TM = Y, Sc, Ti) compounds are structurally and mechanically stable from 0 to 100 GPa. The order of hardness from high to low is TiB2 > ScB2 > YB2. Both TiB2 and ScB2 belong to the type of superhard materials at 0 GPa, but YB2 is not. These materials soften with pressure increasing, especially for ScB2, which changed from superhard to hard material at about 80 GPa. The Pugh and Poisson ratio indicated that they all have a brittle behaviour under pressure, and YB2 is more prone to ductility than ScB2 and TiB2. The bond calculation indicates that all bond lengths decrease monotonously under pressure, and the TM–B bond is more sensitive to pressure. The relationship of bond lengths for TM–B and B–B are YB2 > ScB2 > TiB2 at the same pressure, which suggests that the shorter bonds may lead to a stronger interaction between atoms. Finally, the effects of pressure on the electronic properties are also investigated in detail. [ABSTRACT FROM AUTHOR]

Weyl semimetals (WSMs) have attracted the attention of the researchers due to their fascinating properties which are analogous to that of three-dimensional graphene. The density functional theory (under generalised gradient approximation (GGA) without spin-orbit coupling, GGA with spin-orbit coupling (GGA + SOC) and GGA with Hubbard correction (GGA + U )) in combination with the stress–strain approach have been utilised to investigate the elastic and mechanical properties of ZrS and ZrTe. The thermodynamic properties have been evaluated using the quasi-harmonic approximations by incorporating GGA, GGA + SOC and GGA + U approaches. The polycrystalline elastic moduli have been calculated using the single-crystal elastic constants and the mechanical stabilities have also been established. Physical parameters, such as Young's modulus, shear modulus, Poisson's ratio, Debye temperature and sound velocities, are also calculated. In addition, the anisotropic elastic properties such as Young's modulus, linear compressibility, shear modulus and Poisson's ratio as well as the anisotropic factors have been visualised in three dimensions (3D) using GGA, GGA + SOC and GGA + U approaches. The theoretical computation of thermodynamic properties such as specific heat, entropy, vibration energy and internal energy as a function of temperature for both Weyl semimetals are investigated and discussed for the first time. The calculated values of Debye temperature for ZrS (ZrTe) are 470.103 K (287.744 K), 486.572 K (298.295 K) and 442.0 K (234.346 K) using GGA approximations without SOC, with SOC and by implementing GGA + U calculations, respectively. Further, it is shown that the value of Debye temperature for ZrS is more than that of ZrTe. Hence, the present study of thermodynamic properties suggests their potential thermoelectric applications at high temperatures. [ABSTRACT FROM AUTHOR]

Double halide perovskites have outstanding properties for optoelectronic and renewable energy applications. In the present work, we have analszed the structural, mechanical, electronic and optical properties of K2BI6 (B = Ti, Zr and Hf) using the density functional theory. The results show that these perovskites have good mechanical stability. K2HfI6 is a direct bandgap semiconductor with a bandgap of 3.150 eV. K2TiI6 and K2ZrI6 are indirect bandgap semiconductors with bandgaps of 1.828 and 2.515 eV, respectively, but they can be regarded as quasi-direct bandgap semiconductors. They also show good light absorption properties in the ultraviolet–visible wavelength range. These properties make K2BI6 (B = Ti, Zr and Hf) perovskites good candidates for photovoltaic and optoelectronic applications, such as solar cells, photocatalysts and detectors. [ABSTRACT FROM AUTHOR]

An empirical relationship has been found to evaluate the bulk modulus (B) and shear modulus (G) with the help of two experimental physical quantities (the melting temperature and the crystal ionicity), which are drawn from various pieces of literature. The PVV theory of crystal ionicity and temperature dependence of elasticity are taken into account for the study. The evaluated bulk modulus and shear modulus values are found to be in excellent conformity with experimental and reported values of other researchers. The current research supports the modelling of emerging semiconductor materials and even understanding of their mechanical properties for photovoltaic, spintronics, LiB systems, FLB phenomenon, and superhard material applications. [ABSTRACT FROM AUTHOR]

This paper aims to solve two problems of the sandwich panel with aluminum honeycomb: material parameters solution and shape control. The accurate material parameters of the sandwich panels are the basis of shape control. Therefore, a mixed numerical-experimental method is proposed to inversely solve equivalent material parameters of the sandwich panel using genetic algorithm (GA) in the first place. Then a high efficiency FE model based on equivalent material parameters is established to study shape control of the sandwich panels. For shape control, the key issue aims to search optimum position and adjustment volume of control points where actuators are installed. Toward the end, the FE simulation method is deployed to optimize actuator position and adjustment volume one by one. Finally, an active control platform based on multi-point adjustment is developed to verify the practicability of the approach proposed in this paper. Through the experiment of shape control, the root mean square (RMS) of surface deviation of sandwich panel is decreased from 62.7μm to 15.5μm. The results show that the shape control can significantly improve the surface accuracy of the sandwich panels, and the validity of equivalent material parameters is also proved from the side.

The current work analyzes the transmission behavior of plane harmonic waves in an isotropic medium. The observation is made for homogeneous type solid in the context of generalized dual phase lag model of thermoelasticity. Concept micro-temperature, where the microelements have different temperatures has also been considered. The basic focus of thework is to predict the influence of initially applied magnetic field on plane waves through the elastic solid. We have made an attempt to find exact solution of the problem using an analytical technique of a normal mode analysis method. The theoretical results are obtained for a generalized solid in order to test the numerical calculation of a magnesium crystal. It is found that the magnetic field reduces the strength of the attenuation factor.

SnS2 is an important disulfide having many excellent properties for application. Here we carried out a firstprinciples study of its electronic, elastic and lattice dynamic properties. The band structure calculated by the HSE06 functional indicates that SnS2 is an indirect band gap semiconductor with a gap of 2.16 eV. Calculated partial density of states and the Mulliken charges imply that SnS2 is an ionic-covalent compound. Studies unveil that SnS2 is mechanically and dynamically stable, but it is easy to crack along the c-axis. Phonons at its Brillouin zone center were assigned by group theory analysis and their frequencies were computed. Investigation of its Born effective charges and dielectric constants reveals that ions have a larger dielectric contribution than electrons in the ab plane, but they almost have no contribution along the c direction. [ABSTRACT FROM AUTHOR]

SnS2 is an important disulfide having many excellent properties for application. Here we carried out a firstprinciples study of its electronic, elastic and lattice dynamic properties. The band structure calculated by the HSE06 functional indicates that SnS2 is an indirect band gap semiconductor with a gap of 2.16 eV. Calculated partial density of states and the Mulliken charges imply that SnS2 is an ionic-covalent compound. Studies unveil that SnS2 is mechanically and dynamically stable, but it is easy to crack along the c-axis. Phonons at its Brillouin zone center were assigned by group theory analysis and their frequencies were computed. Investigation of its Born effective charges and dielectric constants reveals that ions have a larger dielectric contribution than electrons in the ab plane, but they almost have no contribution along the c direction. [ABSTRACT FROM AUTHOR]

In this paper, uniaxial material properties, creep resistance and impact energy of the austenitic heat-resistant steel (1.4841) are experimentally determined and analysed. Engineering stress–strain diagrams and uniaxial short-time creep curves are examined with computer-controlled testing machine. Impact energy has been determined and fracture toughness assessed. Investigated data are shown in the form of curves related to ultimate tensile strength, yield strength, modulus of elasticity and creep resistance. All of these experimentally obtained results are analysed and may be used in the design process of the structure where considered material is intended to be applied. Based on these results, considered material may be classified as material of high tensile strength (688 MPa/293 K; 326 MPa/923 K) and high yield strength (498 MPa/293 K; 283 MPa/923 K) as well as satisfactory creep resistance (temperature/stress →$ \to $strain (%) at 1,200 min: 823 K/167 MPa →$ \to $0.25 %; 923 K/85 MPa →$ \to $0.2 %).

In the case of technologically important quaternary alloys, structural and optoelectronic properties have been calculated with density functional theory (DFT)-based full-potential linearised augmented plane-wave (FP-LAPW) approach. The Perdew–Burke–Ernzerhof generalised gradient approximation (PBE-GGA) for structural properties and both the modified-Becke–Johnson (mBJ) and Engel and Vosko GGA (EV-GGA) for optoelectronic properties are employed to calculate the respective exchange-correlation potentials. Each specimen within the quaternary system is a direct band-gap – semiconductor. The lattice constant decreases, while bulk modulus and band gap increase nonlinearly with increasing anionic (S) concentration at each cationic (Mg) concentration. On the other hand, nonlinear increment in lattice constant and band gap, but decrement in bulk modulus is found with increase in cationic concentration at each anionic concentration. Calculated contour maps for lattice constants and energy band gaps would be useful in fabricating new quaternary alloys with preferred optoelectronic features. Optical properties of the specimens within the quaternary system show several interesting features. , 4p and 4p optical excitations contribute intense peaks in each spectrum. The composition dependence of each calculated zero-frequency limit shows opposite trend, while each calculated critical point shows similar trend of composition dependence of band gap. Moreover, calculations suggest the possibility of growth of several cubic quaternary specimens on GaAs and InP substrates. [ABSTRACT FROM AUTHOR]

This study aims to obtain travelling wave solutions of the doubly dispersive equation in nonlinear dynamic elasticity by the sine-Gordon expansion method. We give physical explanation of the presented solutions under suitable parameters via the 3D, 2D and contour simulations. [ABSTRACT FROM AUTHOR]

The paper presents computation of second- and third-order elastic constants of Laves phase compounds ScOs2 and YOs2 at room temperature using Lennard-Jones potential model. The thermal relaxation time, ultrasonic velocity, ultrasonic attenuation and other related thermo-physical parameters (Debye average velocity, Debye temperature, thermal conductivity, specific heat and thermal energy density) are also calculated using second- and third-order elastic constants. The obtained elastic and ultrasonic properties of chosen compounds have been likened with the properties of other hexagonal structured materials for complete analysis and characterization. [ABSTRACT FROM AUTHOR]

The paper presents and analyzes the experimental results of the effect of elevated temperatures on the engineering properties of steel 42CrMo4. Experimental data relating to the mechanical properties of the material, the creep resistance as well as Charpy impact energy. Temperature dependence of the mentioned properties is also shown. Some of creep curves were simulated using rheological models and an analytical equation. Finally, an assessment of fracture toughness was made that was based on experimentally determined Charpy impact energy. Based on the obtained results it is visible that the tensile strength (617 MPa) and yield strength (415 MPa) have the highest value at the room temperature while at the temperature of 700 °C (973 K) these values significantly decrease. This steel can be considered resistant to creep at 400 °C (673 K), but at higher temperatures this steel can be subjected to low levels of stress in a shorter time.

Germanium is an important semiconductor having abundant phases of scientific interest. In this work, we studied the structural, electronic, vibrational, elastic and thermal conductivity properties of a tetragonal germanium via first-principles calculations. The results indicate that it is dynamically stable and there is a breathing vibrational mode at its Brillouin zone center. It is a weak metal according to the GGA-based calculation, but an indirect bandgap semiconductor with a gap of 0.24 eV based on the HSE06-functional calculation. According to the calculations performed by the HSE06 functional, both positive and negative hydrostatic pressures can first alter the band gap to be direct and then metallic. The crystal is mechanically stable but anisotropic. Its hardness is predicted to be 8.2 GPa, slightly lower than that of cubic diamond-type Ge. Based on the calculated phonon dispersion curves, its thermal conductivity as a function of temperature is predicted, giving a value of about 13.5 W m-1 K-1 at 300 K. [ABSTRACT FROM AUTHOR]

The elastic, mechanical and thermal properties of isostructural and isoelectronic nonmagnetic REPt3 (RE = Sc, Y and Lu) intermetallic compounds, which crystallize in AuCu3-type structure, are studied using first principles density functional theory based on full potential linearized augmented plane wave method. The calculations are carried out within PBE-GGA, WC-GGA and PBE-sol GGA for the exchange correlation potential. Our calculated ground state properties such as lattice constant (ao), bulk modulus (B) and its pressure derivative (B′) are in good agreement with the available experimental and other theoretical results. We first time predict the elastic constants for these compounds using GGA approximations. All the compounds are found to be ductile in nature in accordance with Pugh’s criteria. The computed electronic band structures show metallic character of these compounds. The charge density plot and density of states of these compounds reveals that the chemical bond between RE and Pt is mainly ionic. The elastic properties including Poisson’s ratio (σ), Young’s modulus (E), shear modulus (GH) and anisotropy factor (A) are also determined using the Voigt-Reuss-Hill averaging scheme. The average sound velocities (vm), density (ρ) and Debye temperature (θD) of these REPt3 compounds are also estimated from the elastic constants. We first time report the variation of elastic constants, elastic moduli, sound velocities and Debye temperatures of these compounds as a function of pressure. [ABSTRACT FROM AUTHOR]

In the present paper study of the high pressure behaviour of aggregated diamond nanorods (ADNRs) and diamond have been carried out. A comparative study of different equations of state is discussed to understand the high pressure behaviour of diamond and the aggregated diamond nanorods. In the present study the usual Tait’s equation of state has been modified to predict the high pressure behaviour of carbon material ADNRs and diamond. The results obtained in the present study are compared with available experimental evidences. Bulk moduli as a function of pressure are also computed for ADNRs and natural diamond in the light of recent investigations. Present study reveals that ADNRs are less compressible than diamond. [ABSTRACT FROM AUTHOR]

Ab initio calculations based on the density functional theory within the fullpotential linearized augmented plane wave method were carried out to investigate the structural stabilities of the different crystallographic phases, the pressure-induced phase transition and the electronic properties of the platinum carbide (PtC) compound. The zinc-blende (ZB), rock-salt (RS), cesium chloride (CsCl), wurtzite (WZ), nickel arsenide (NiAs), lead monoxide (PbO) and the tungsten carbide (WC) phases were considered. The exchange and correlation potential was treated by the generalized-gradient approximation using the Perde-Burke-Ernzerhof parameterization. The thermodynamic properties such as variation of the bulk modulus, lattice constant, heat capacity, thermal expansion and Debye temperature versus pressures and temperatures are investigated. The band structure results show the metallic character of the PtC compound in all the considered phases and the present study also shows that the PtC compound crystallizes in the ZB phase at ambient conditions. The theoretical transition pressures from the ZB to RS for the NiAs, PbO and CsCl transformations were also computed. [ABSTRACT FROM AUTHOR]

The plane wave pseudo-potential method within density functional theory has been used to calculate the structural and elastic properties of ABC semiconductors. The electronic band structure, density of states, lattice constants (a and c), internal parameter (u), tetragonal distortion (η), energy gap (E), and bond lengths of the A-C (d) and B-C (d) bonds in ABC semiconductors have been calculated. The values of elastic constants (C), bulk modulus (B), shear modulus (G), Young's modulus (Y), Poisson's ratio (υ), Zener anisotropy factor (A), Debye temperature (ϴ) and G/B ratio have also been calculated. The values of all 15 parameters of CuTlS and CuTlSe compounds, and 8 parameters of 20 compounds of ABC family, except AgInS and AgInSe, have been calculated for the first time. Reasonably good agreement has been obtained between the calculated, reported and available experimental values. [ABSTRACT FROM AUTHOR]

The structural, electronic, elastic, dynamic and optical properties of the ternary chalcopyrite compound MgGeSb were studied by using the density functional theory (DFT) framework for different exchange-correlation functionals. The obtained equilibrium structural parameters are in good agreement with the available theoretical result. After considering the electronic band structure and electronic density of states (DOS) calculation; this compound is a semiconductor as suggested in the previous work. However; all considered functionals underestimate considerably the electronic band gap energies compared with the experimental results. We have predicted single-crystal elastic constants and related properties such as Young's modulus, Poisson ratio, shear modulus and bulk modulus. Optical properties such as the dielectric function, refractive index, extinction index have been calculated in the range of 0-20 eV. The obtained results can facilitate an assessment of possible applications of MgGeSb. [ABSTRACT FROM AUTHOR]

The main goal of nanoindentation tests is to obtain elastic modulus and hardness of the specimen material from load-displacement measurements. With this study, it was aimed to establish a quantitative relationship between the nanomechanical properties of commonly used dental cements in comparison to a newly developed crown cement and to predict its performance potential. Nanomechanical properties of polycarboxylate cement (PCC), glass-ionomer cement (GIC), dual-cure self-adhesive cement (SAC) and a newly developed glass-carbomer cement (GCC) were investigated by nanoindentation tests. All samples were fabricated according to their respective manufacturer's instructions. Available damage on the surface due to manipulation was removed by grinding with 1200, 2400 and 4000 grit sandpaper, and then polishing on 6, 3, and 1 μm diamond-lap-wheel was performed. Nano-mechanical measurements were done using nanoindenter machine with resolution less than 1 nN and displacement resolution of 0.04 nm. Berkovich diamond indenter tip was used for the nanoindentation tests. For each indentation, a set of nanoindentation tests at least on 6 different locations per specimen surface were performed to obtain more representative mean results. Indentation test load-displacement curves were analysed using Oliver-Pharr method, and one-way ANOVA or Kruskal-Wallis test, following Kolmogorov-Smirnov and Shapiro-Wilk, was used to compare the results. Nanohardness (Hnano) values were 0:52±0:25, 0:45±0:18, 1:03±0:82 and 0:43±0:18 GPa for GIC, GCC, PCC, and SAC, respectively. Reduced elastic modulus (Er) values were 9:51 ± 6:17, 11:77 ± 5:04, 27:37 ± 20:61, 10:33 ± 5:08 GPa for GIC, GCC, PCC, and SAC, respectively. There was no statistical difference between the tested materials. PCC was the hardest, and GIC was the least hard material, whereas the newly developed GCC was the second, in terms of Hnano, before SAC. PCC also had the highest Er mean, compared to the other dental crown cements, suggesting lower elastic properties. SAC was more elastic than GCC and less elastic than GIC. GCC had the second highest Er, standing closer to SAC and GIC. Within the limitations of the current study, it can be concluded that the newly developed glass-carbomer cement is comparable to the other tested commonly used dental crown cements, regarding Hnano and Er. [ABSTRACT FROM AUTHOR]

The thin layers of (Sn,Mn)Te solid solution were grown by molecular beam epitaxy onto (111)-oriented BaF2 substrates and characterized by scanning electron microscopy, atomic force microscopy, energy dispersive X-ray spectrometry, and X-ray diffraction methods. The epitaxial character of the growth was confirmed. All the layers exhibited a regular (fcc) structure of the rock-salt type and were (111)-oriented, their thickness was close to about 1 µm. The layers contained up to 8% of Mn. The microhardness and the Young modulus values were determined by the nanoindentation measurements. The Berkovich type of the intender was applied, the maximum applied load was equal to 1 mN. The results of measurements demonstrated a lack of the composition dependence of the Young modulus value. A slight increase of the microhardness value with an increasing Mn content in the (Sn,Mn)Te solid solution was observed. [ABSTRACT FROM AUTHOR]

The double perovskite oxides have diverse applications in the fields such as magnetism and spintronics. We report on the structural, elastic, electronic and magnetic properties of double perovskites BaXOsO (X = Li, Na, Ca) calculated using the full-potential linearized augmented plane wave method. For the treatment of the exchange-correlation energy, the generalized gradient approximation (GGA) of Wu and Cohen (WC-GGA), Perdew, Burke and Ernzerhof (PBE-GGA), Engel-Vosko's (EV-GGA) and GGA plus Hubbard U parameter (GGA+ U) have been utilized. The calculated lattice constant, band structure and density of states are found in good agreement with the existing experimental and theoretical results. In particular, we present theoretical calculation of the bulk modulus of these compounds which, according to our knowledge, has not been reported. The calculation of elastic parameters suggests that these compounds possess ductile nature. The GGA+ U approach provides better band gap results as compared to others approximations. The density of states shows that Ba-5 p, Ba-4 f, Os-5 d and O-2 p states contribute majorly in the conduction and valence bands. The calculated magnetic moments of all these compounds reveal ferromagnetic nature. These compounds seem to possess half-metallic properties which may make them useful candidates for spintronics device applications. [ABSTRACT FROM AUTHOR]

The structural parameters, electronic, elastic, hardness and optical properties of oP-type RuB ( Space group Pnma, No: 62) are investigated by means of density functional theory method within local-density approximation as a function of pressure. It is shown that the results at 0 GPa pressure are in good agreement with related theoretical and experimental data. The pressure dependence of elastic constants, special bond lengths, Mulliken bond populations, hardness, energy band gaps, charge densities and optical properties such as dielectric function, absorption coefficient, reflectivity function, extinction coefficient, refractive index, energy loss spectrum of oP-type RuB have been investigated. It is observed that the oP-type RuB compound exhibits anisotropic compressibility under hydrostatic pressure: c-direction is more compressible than a- and b-directions, due to the different bond stiffness and bond angle changes. From calculated partial density of states, Mulliken populations and 2D/3D electron densities, the nature of chemical bonding for RuB can be recognized as a combination of partially covalent, ionic and metallic bonds. The calculated hardness value shows that oP- type RuB is hard material. [ABSTRACT FROM AUTHOR]

The first principles calculations were performed by the linearized augmented plane wave (LAPW) method as implemented in the WIEN2K code within the density functional theory to obtain the structural, electronic and optical properties of CdSiP 2 in the body centered tetragonal (BCT) phase. The six elastic constants ( C 11 , C 12 , C 13 , C 33 , C 44 and C 66 ) and mechanical parameters were presented and compared with the available experimental data. The thermodynamic calculations within the quasi-harmonic approximation is used to give an accurate description of the pressure-temperature dependence of the thermal-expansion coefficient, bulk modulus, specific heat, Debye temperature, entropy Grüneisen parameters and hardness. Further, CdSiP 2 solar cell devices have been modeled; device physics and performance parameters are analyzed for zinc chalcogenide (ZnX; X = Se, Te) buffer layers. Simulation results for CdSiP 2 thin layer solar cell show the maximum efficiency (25.7%) with ZnSe as the buffer layer. [ABSTRACT FROM AUTHOR]

In this study, the structural, elastic, electronic, and bonding nature of AgZn in B2 structure under pressure have been investigated by performing first principles calculations using density functional theory. The exchange-correlation potentials were treated within the generalized gradient approximation. The calculated quantities agree well with the available results. The electronic properties, such as band structure and density of states reveal that AgZn is metallic in nature with a large overlap at the Fermi level. The single-crystal elastic stiffness constants of AgZn are investigated using the stress-strain method. Present results for elastic constants show that AgZn is mechanically stable. The chemical bonding is interpreted by calculating the density of states and electron density distribution analysis. AgZn has ionic bonding characteristic. [ABSTRACT FROM AUTHOR]

We present an ab initio calculations to investigate the structural, electronic and elastic properties of BeX (X = Co, Ni, Cu and Pd) intermetallic compounds using full potential linearized augmented plane wave method. The exchange correlation energy is described in generalized gradient approximations. The ground-state properties such as lattice parameter ( a), bulk modulus ( B) and pressure derivative of bulk modulus ( B') have been determined. The band structure and density of states histograms are plotted which reveal the metallic nature for all the four compounds. A special attention has been paid to the determination of the second order elastic constants. By calculating bulk-to-shear modulus ratio ( B/ G) and Cauchy pressure ( C- C), ductility or brittleness of these intermetallics is determined. Pressure dependences of elastic constants and sound wave velocities including Debye temperature are also investigated. [ABSTRACT FROM AUTHOR]

The ductility and hardness behaviour of NbTiN ( x = 0, .25, .5, .75 and 1) ternary alloy has been studied. Bulk modulus, Young's modulus, shear modulus, Poisson's ratio and anisotropy energy have been calculated. Analysis of G/B and Cauchy's pressure shows that TiN is brittle in nature in good agreement with other theoretical results. Systematic addition of Nb with TiN shows that NbTiN is ductile. The charge density plot shows weak directional contours that enclose Ti and N due to the ductile behaviour of the alloy, namely NbTiN. The estimated hardness of NbTiN is 19.78 GPa, which is 70 % of hardness value of TiN (29.4 GPa) and thus addition of niobium enhances the ductility of TiN. The Debye temperature of the present alloy system is also reported. [ABSTRACT FROM AUTHOR]

The phase stability, structural, magnetic, electronic, mechanical and thermal properties of cubic GdX (X = In, Sn, Tl and Pb) rare earth intermetallics, which crystallize in AuCu-type structure, have been investigated using first-principles density functional theory based on full-potential linearized augmented plane wave method. The calculations are carried out within local spin approximation and local spin approximation along with Hubbard term for the exchange correlation potential in order to obtain the appropriate results. The computed lattice parameters using local spin approximation along with Hubbard term are in good agreement with the experimental results. It is lucid from the magnetic stability curves that all these studied compounds are magnetic in nature. The electronic band structures as well as density of states reveal that the studied compounds show metallic behavior under ambient conditions. The results of cohesive energy indicate that these compounds are stable in AuCu phase at ambient conditions and that the stability of GdSn is the strongest among the investigated cubic GdX compounds. We, for the first time, predict the second-order elastic constants for these compounds. All these GdX compounds, except GdIn, are found to be ductile in nature in accordance with Pugh's criteria. Poisson's ratio, Young's modulus, shear modulus, anisotropy factor, average sound velocities, density and Debye temperature of these GdX compounds are also estimated for the first time. [ABSTRACT FROM AUTHOR]

The ab initio calculations were performed for CdGeP 2 chalcopyrite in the body centered tetragonal (BCT) phase in an attempt to calculate the structural, electronic and optical properties by linearized augmented plane wave (LAPW) method as implemented in the WIEN2K . Furthermore, optical features such as dielectric functions, refractive indices, extinction coefficient, optical reflectivity, absorption coefficients, optical conductivities, were calculated for photon energies up to 40 eV. The six elastic constants (C 11 , C 12 , C 13 , C 33 , C 44 and C 66 ) and mechanical parameters were presented and compared with the available experimental data. The thermodynamic calculations within the quasi-harmonic approximation is used to give an accurate description of the pressure–temperature dependence of the thermal-expansion coefficient, bulk modulus, specific heat, Debye temperature, entropy and Grüneisen parameters. Based on the semi-empirical relation, we have determined the hardness of the materials for the first time at different pressure (0–8 GPa) and temperature (0–1000 K). Further, CdGeP 2 solar cell devices have been modeled; device physics and performance parameters are analyzed for zinc chalcogenides (ZnX; X=S, Se, Te) buffer layers. Simulation results for CdGeP 2 thin layer solar cell show the maximum efficiency (22.6%) with ZnSe as the buffer layer. [ABSTRACT FROM AUTHOR]

Structural, elastic, electronic and magnetic properties of the cubic perovskites SmMO ( M = V, Fe and Co) are investigated by using the density functional theory. The exchange correlation potential of GGA+ U is employed in the present calculations to treat the f-state electrons of Sm atom properly. The structural parameters of these compounds are also evaluated by analytical techniques. The computed structural parameters by both GGA and analytical model are in good agreement with the experimental results. Furthermore, the calculated tolerance factors confirm the theoretically observed cubic structure for all the three compounds. The evaluated critical radii of the compounds provide information about the oxygen migration energy and ion conductivity. The compounds are elastically stable and ductile in nature. The spin-polarized band structures show that the compounds are metallic. The total and partial densities of states show that the compounds are ferromagnetic metals. The calculated magnetic moments of these compounds also reveal that they are ferromagnets. [ABSTRACT FROM AUTHOR]

The electronic, mechanical, and thermodynamic properties of europium carbide (EuC2) are investigated using first-principles density functional theory within the generalized gradient approximation. The calculated elastic constants indicate that EuC2 is mechanically stable. The shear modulus, Young's modulus, Poisson's ratio, the bulk modulus - shear modulus ratio, shear anisotropy, and elastic anisotropy are also calculated. Finally, we obtain the Vickers hardness, averaged sound velocity, longitudinal sound velocity, transverse sound velocity, Debye temperature, melting point, and thermal conductivity of EuC2. [ABSTRACT FROM AUTHOR]

This paper reports an analysis on the high-pressure and temperature structural phase transition of praseodymium pnictides (phosphide: PrP and arsenide: PrAs). The Realistic Interaction Potential Approach (RIPA) model has been developed and used to study the structural and elastic properties. Phase transition pressures are associated with a sudden collapse in volume. Phase transition pressures have been reported at high temperature range 0–1000 K. The phase transition pressures and associated volume collapses obtained from present potential model show a generally better agreement with available experimental data than others. The elastic constants and their pressure derivatives are also reported. The temperature and pressure behaviors of bulk modulus for the present compounds are also discussed. [ABSTRACT FROM AUTHOR]

Investigations into the electronic properties, elastic properties, and ideal tensile strengths for Ti2AlN and Ti4AlN3 were conducted using first-principles density functional calculations. The electronic band structures and density of states show metallic conductivity in which Ti 3d states dominate for Ti2AlN and Ti4AlN3. Moreover, the hybridization peak of Ti 3d and N 2p lies at a lower energy than that of Ti 3d and Al 3p, which suggests that the Ti 3d - N 2p bond is stronger than the Ti 3d - Al 3p bond. The variations of elastic constants with pressure indicate that Ti2AlN and Ti4AlN3 possess higher mechanical stability in the pressure range 0-100 GPa. By calculating the bulk-modulus-to-shear-modulus ratio and Cauchy pressure, we predict that Ti2AlN and Ti4AlN3 are brittle. We show that the structural failure of these ternary compounds can be ascribed to the breakage of weak Ti-Al bonds under uniaxial tension and that layered structural stability is determined by the strength of the Ti-Al bond under tensile deformation. [ABSTRACT FROM AUTHOR]

Polypropylene (PP) and polyimide (PI), which belong to entirely different classes of polymers, are irradiated by Co-60 gamma radiation under similar doses and similar conditions in the dose range varying from 57.6 to 230.4 kGy. The radiation responses of these two polymers are analyzed by various characterizations such as Fourier transform infrared, UV–visible, energy-dispersive spectroscopy, X-ray diffraction, scanning electron microscopy and contact angle. PP shows substantial modifications in its structure and properties while in the same dose range, PI shows remarkable stability. These two different responses are interpreted in terms of physicochemical structure and properties of these polymers. [ABSTRACT FROM PUBLISHER]

By irradiating two macromolecules, namely polypropylene and polyimide having notably different physicochemical properties, with the same radiation under identical conditions, it is inferred that the mechanical and thermal degradation or the stability of the macromolecule exposed to high-energy radiation strongly correlates with its physicochemical structure. This is well supported by two distinct characterizations, namely stress–strain analysis and thermogravimetric analysis. [ABSTRACT FROM AUTHOR]

Abstract: The high-pressure compression behaviour of the nanomaterials 3C-SiC, Zr0.1Ti0.9O2, CuO, AlN, TiO2 (anatase), TiO2 (rutile), α-Fe2O3, γ-Fe2O3, ɛ-Fe and Rb3C60 was studied in two theoretical equation of state (EOS) models. In the first model, we considered the pressure to be quadratic in terms of relative volume change, while in the second model pressure was considered to be quadratic in density. The experimental data show that the second model gives better results. The two models were also studied for their suitability in cases of very high compression. [Copyright &y& Elsevier]

We have investigated the elastic and thermodynamic properties of transition metal carbides (TiC, ZrC, HfC, VC, NbC, and TaC) using the three body force potential model and density functional theory based ab initio approach. The computed second-order elastic constants ( C11, C12, C44) are in close agreement with the available experimental as well as theoretical results. The other related elastic parameters ( B0, B0′, CS, CL, G, ν, E, A, β, ξ, λ, Cauchy pressure ( C12 - C44), B0/ G, and E/ ρ ratio) have also been computed successfully. The calculated Debye temperatures are in reasonably good agreement with the available data. [ABSTRACT FROM AUTHOR]

The phase transformation from α to β poly(vinylidene fluoride) (PVDF) through a stretching process at different temperatures was investigated. Samples of originally α-PVDF were stretched uniaxially at different temperatures at draw ratios from 1 to 5. The stretched samples were studied and characterized by infrared spectroscopy, scanning electron microscopy, and differential scanning calorimetry. The maximum β-phase content was achieved at 80°C and a stretch ratio of 5, but the samples still showed 20% of the original α-phase. Accompanying the phase transformation, an orientation of the polymer chains was observed. The stretching process also influenced the degree of crystallinity of the polymer. Poling of the samples also improves the α- to β-phase transformation. [ABSTRACT FROM AUTHOR]