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First-principles calculations of electronic parameters, mechanical and dynamical stabilities on superconducting properties of the body-centered tetragonal intermetallic lanthanum dicarbide LaC2 have been reported at zero and high pressures. The investigated properties have been established through both full-potential-linearized augmented plane wave (FP-LAPW) and plane-wave pseudopotential (PW-PP) approaches, in conjunction with the generalized gradient approximation (GGA). Our investigations validate that the LaC2 crystal has a mechanical and dynamical stability under normal conditions. The generalised mechanical stability criteria applied to compressed LaC2, suggest that the compound remains stable for pressures below 18.30 GPa. The evaluated superconducting critical temperature Tc and the electron–phonon coupling parameter λ at zero pressure are found to be in excellent concordance with the experimental data. Furthermore, at elevated pressures, Tc and λ are predicted to decrease and the normalised specific heat jump remains unchanged. [ABSTRACT FROM AUTHOR]

This work aims to study the structural and elastic properties of tetragonal lead dioxide (β-PbO2) material using first-principles calculations. Features such as lattice parameters, bulk modulus and its first pressure derivative, elastic constants, mechanical parameters, sound velocities, Debye temperature and melting temperature have been investigated, and their dependence on pressure in the range 0–1 GPa has been analyzed and discussed. Upon compression, the stiffness of the material of interest is found to become larger as compared to that at zero pressure. Moreover, its tetragonal structure fulfills the mechanical stability criteria in all studied pressure range. Besides, the analysis of Pugh's ratio shows that PbO2 behaves in a ductile manner. [ABSTRACT FROM AUTHOR]

Abstract We investigate the structural phase transition, elastic constants and their related mechanical properties, stability and optical response of zinc-blende MnSe by the pseudopotential plane-wave method within the generalized gradient approximation using different parameterizations. At zero pressure, our findings show generally a reasonably good accord with available data reported in the literature. Nevertheless, in most cases, our results are predictions. The transition pressure from zinc-blende phase to NaCl phase is found to occur at pressure of 1 GPa. The mechanical stability criteria are fulfilled for all pressures being considered in the present work. All features of interest are affected by the presence of pressure leading to new physical properties of the material in question. Highlights • Phase transition pressure from zinc-blende phase to NaCl phase for MnSe. • Mechanical stability of MnSe under pressure. • Optical spectra of MnSe at zero and under pressure. [ABSTRACT FROM AUTHOR]

The pressure dependence of exciton properties, optical phonon modes, polaron characteristics and plasma frequency of GaSb has been investigated using a pseudopotential approach combined with Harrison and Adachi's models. The obtained results show reasonable accord with data available in the literature. The enhanced pressure from 0 to 40 kbar increases the exciton reduced mass monotonously and in a non-linear way. The screening effect makes the Bohr radius much larger than the lattice parameter of these semiconductor materials. The phonon frequency modes increase with increasing pressure. This is due to the pressure effect that brought atoms closer to each other and thus they sit in steeper potential wells. The Fröhlich coupling constant decreases monotonously with increasing pressure. This reflects the reduction of the lattice asymmetrical local deformation when GaSb is subjected to pressure. The applied pressure makes the plasma system of GaSb creates longer wavelengths which give ions a large amount of kinetic energy. The information obtained from this contribution may become good guidance for use of the material in question in several device applications, e.g., in infrared optical sources and thermo photovoltaic systems. [ABSTRACT FROM AUTHOR]

Abstract: Based on the pseudopotential approach, the lattice vibration and polaron properties in InP under pressure up to 8GPa have been investigated. At zero pressure, our calculated values for all features of interest are in reasonable agreement with data available in literature. Upon compression, the optical phonon modes at Γ point in the Brillouin zone are shifted towards high energies and their frequencies display a blueshift with rising pressure. The splitting of the longitudinal and transverse optical phonons narrows under pressure, indicating thus a decrease of the ionicity of InP crystal with pressure. It is observed that all physical quantities being studied in this contribution behave monotonically upon compression. To the best of the author''s knowledge, the pressure dependence of the polaron properties for InP in the present study is reported for the first time. [Copyright &y& Elsevier]