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Structural, electronic, elastic and thermal properties of Al₄Si₂C₅ under constant pressure were investigated by using first-principles theory. The total volume of the cell decreased by almost 15.7% under 40 GPa which is smaller than that of Al₄SiC₄ (16%), while the linear compressibility along $a$- or $b$-axis direction showed better anti-deformation behavior than that of along $c$-axis direction. The peak heights of total density of state (TDOS) and partial density of state (PDOS) curves of Al₄Si₂C₅ are slightly lowered with forced high pressure. Meanwhile, the mechanical properties of Al₄Si₂C₅-like elastic constants and elastic moduli accelerate with the pressure increasing from 0 GPa to 40 GPa; the thermal expansion coefficient $\alpha$ increases rapidly at lower temperature and this tendency gradually approaches a linear increase when the temperature is above 1000 K. At particular temperature, $\alpha$ decreases continuously with the pressure accelerating. Heat capacity at constant volume ($C_V)$ with pressure was also evaluated, the results displayed that $C_V$ is sensitive with the temperature rather than the pressure. The elastic anisotropy and Debye temperature with pressure were successfully obtained and discussed.

A realistic interaction potential model (RIPM) has been formulated to theoretically predict the pressure-induced phase transition, elastic properties and thermophysical properties of AlAs and AlSb, including temperature effect (300 K). This model exhibits a better agreement with the available experimental rather than theoretical data for obtained calculations of phase transition pressures and volume collapses. We have achieved elastic moduli, anisotropy factor, Poisson’s ratio, Kleinman parameter, on the basis of the calculated elastic constants. Apparently, this is the first time when thermophysical properties of these compounds are explored at temperature effect by using a single model. Our results are justified by available measured and other reported data which support the validity of our model.

The manganite oxides, YMnO₃ and ErMnO₃ having hexagonal structures were prepared by the solid state reaction method. After characterizing these materials by studying their various physical properties such as lattice parameters, X-ray density, bulk density etc., ultrasonic velocity measurements were carried out over a temperature range 80–300 K to investigate their elastic behavior. As the materials are porous, the measured elastic moduli were corrected to zero porosity. Using the room temperature elastic moduli, Debye temperature values of both the manganites have also been obtained. Surprisingly it has been found that the Young's moduli of both the materials increase continuously with decreasing temperature. A qualitative explanation for the observed behavior is offered.

The longitudinal (V_l) and shear (V_s) wave velocities of Praseodymium substituted YB₂Cu₃O_7-δ high temperature superconductors were determined at room temperature by the pulse transmission technique. The values of Young's (E), rigidity (n) and bulk (k) moduli have been corrected to zero porosity. The zero porous corrected values of the elastic moduli are found to increase with increasing Praseodymium concentration. A linear relationship between the Debye temperature (θ_D) and average sound velocity (V_m) has also been observed and the behavior is explained qualitatively.

A theoretical study is conducted by first-principles theory to study the structural, electronic, elastic and thermal properties of Al₄SiC₄, Al₄C₃ and 4H-SiC phases under pressure. The calculated results indicated that the volumetric shrinkage of Al₄SiC₄ declines to 16% compared with 4H-SiC for 12% and its length of lattice parameter along c-axis decreases faster than that of along other axes in cell structures. The mechanical properties of Al₄SiC₄ like elastic constants and elastic moduli increase continuously under pressure. The thermal expansion coefficient of three compounds under pressure are studied first. When temperature is lower than 500 K, the coefficient increases rapidly first then gradually tends to a linear accession at higher temperature and the propensity of increment becomes moderate. The $C_V$ data decreases slightly with pressure but increases dramatically with temperature for all compounds.

The conformational properties and elastic behaviors of protein-like single chains in the process of tensile elongation were investigated by means of Monte Carlo method. The sequences of protein-like single chains contain two types of residues: hydrophobic (H) and hydrophilic (P). The average conformations and thermodynamics statistical properties of protein-like single chains with various elongation ratio λ were calculated. It was found that the mean-square end-to-end distance 〈R²〉_r increases with elongation ratio λ. The tensor eigenvalues ratio of decreases with elongation ratio λ for short (HP)_x protein-like polymers, however, the ratio of increases with elongation ratio λ, especially for long (H)_x sequence. Average energy per bond 〈U〉 increases with elongation ratio λ, especially for (H)_x protein-like single chains. Helmholtz free energy per bond also increases with elongation ratio λ. Elastic force (f), energy contribution to force (f_U) and entropy contribution to force (f_S) for different protein-like single chains were also calculated. These investigations may provide some insights into elastic behaviors of proteins.

The elastic behavior of protein-like chains was investigated by using the Pruned-Enriched-Rosenbluth Method (PERM). Three typical protein-like chains such as all-α, all-β, and α + β (α/ β) proteins were studied in our modified orientation dependent monomer-monomer interaction (ODI) model. We calculated the ratio of <R²>/N and shape factor <δ*> of protein-like chains in the process of elongation. In the meantime, we discussed the average energy per bond <U>/N, average contact energy per bond <U>_c/N, average helical energy per bond <U>_h/N and average sheet energy per bond <U>_b/N. Three maps of contact formation, α-helix formation, β-sheet formation were depicted. All the results educe a view that the helix structure is the most stable structure, while the other two structures are easy to be destroyed. Besides, the average Helmholtz free energy per bond <A>/N is was presented. The force f obtained from the free energy was also discussed. It was shown that the chain extended itself spontaneously first. The force was studied in the process of elongation. Lastly, the energy contribution to elastic force f_u was calculated too. It was noted that f_u for all-β chains increased first, and then decreased with x₀ increasing.

The electronic structure, mechanical property and thermal expansion of yttrium oxysulfide are calculated from first-principles using the theory of density functional. The calculated cohesive energy indicates its thermodynamic stable nature. From bond structure, the calculated bandgap is obtained as 2.7 eV; and strong covalent bonds exist between Y and O atoms intra 2D [Y–O] layer in material, while relatively weak covalent bonds also exist inter 2D [Y–O] layer and S atoms. From simulation, it is found that the bulk modulus is about 119.4 GPa for the elastic constants, and the bulk modulus shows weak anisotropy because the surface contours of them are close to a spherical shape. The calculated B/G clearly implies its ductile nature, and the Y₂O₂S phase can also be compressed easily. The temperature dependence of thermal expansions is mainly caused by the restoration of thermal energy due to lattice excitations at low temperature. When the temperature is very high, the thermal expansion coefficient increases linearly with temperature increasing. Meanwhile, the heat capacities are also calculated and discussed by thermal expansion and elasticity.