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    Thermoelastic properties of ULE® titanium silicate glass
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    SnO 2 has various specific and unique properties, which make this material very useful for many applications. The elastic constants of materials are very important because they are closely associated with the mechanical, physical and chemical properties. The structural and elastic constants of SnO 2 were investigated using density functional theory (DFT) as implemented in VASP software. The lattice parameters, atomic positions and elastic constants were studied up to pressure of 18 GPa. The calculated elastic constants indicate that SnO 2 is mechanically stable. Some fundamental physical quantities such as bulk modulus, Debye temperature, Poisson’s ratio, Young's modulus, shear modulus, and crystal anisotropy were derived calculated data. The phase transition from CaCl 2 – type to α-PbO 2 structure is obtained at 12.13 GPa. The Debye temperature of SnO 2 was computed from the elastic moduli and sound velocities. The computed average linear compressibility of α-PbO 2 structure is 1.90 TPa -1 in the x, y and z direction at ambient pressure. Also, the pressure-induced lattice (elastic) constants were fitted to the regression equation in order to make direct comparison to results obtained by other calculations. The results were compared with available theoretical and experimental data.
    Debye model
    Lattice constant
    Shear modulus
    Poisson's ratio
    Debye
    The equilibrium lattice constants, bulk modulus, shear modulus, elastic constants and Debye temperature of LaNi4.75Sn0.25 under pressure are calculated using the full-potential linearized augmented plane wave (FP-LAPW) method as well as the quasi-harmonic Debye model. The results at zero pressure are in excellent agreement with the experimental data. The Sn atom is found to occupy the equivalent 3g site (0.5a, 0.75b, 0.5c) in the quadruple cell. The Debye temperature of LaNi4.75Sn0.25 is lower than that of LaNi5. The dependences of bulk modulus on finite temperature and on finite pressure are also investigated. The results show that the bulk modulus B increases monotonously as pressure increases.
    Debye model
    Shear modulus
    Debye function
    Lattice constant
    Debye
    Lattice (music)
    Abstract First-principles calculations are performed to study the structural and elastic properties, sound velocities, and Debye temperature of rocksalt-structured copper monochloride (CuCl) and copper monobromide (CuBr). The structural parameters, elastic constants, longitudinal, transverse, and average elastic wave velocities, and the Debye temperature in the pressure range 10–20 GPa are successfully predicted and analysed. The variation of the elastic constants and bulk modulus as a function of pressure is found to be non-linear for CuCl and almost linear for CuBr. Based on the obtained values of the elastic constants, the bulk modulus, the isotropic shear modulus, Young’s modulus, Poisson’s ratio, and Pugh’s ratio of the aggregate materials are also investigated. The analysis of Poisson’s and Pugh’s ratios shows that these materials become ductile for pressures in the range 10–20 GPa. The evolution of the longitudinal sound velocity under pressure indicates the hardening of the corresponding phonons in both materials.
    Debye model
    Poisson's ratio
    Shear modulus
    Atmospheric temperature range
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    Debye model
    Lattice constant
    Grüneisen parameter
    Poisson's ratio
    Atmospheric temperature range
    Citations (13)