Ab initio calculations of elastic constants and thermodynamic properties of Li2O for high temperatures and pressures

Li, Xiaofeng; Chen, Xiangrong; Meng, Chao; Ji, Guang-Fu

doi:10.1016/j.ssc.2006.06.013

Cited by 47 publications

(14 citation statements)

References 22 publications

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“…SrX lattice is thus thermally softened and mechanical stiffened. The normalized volume V T /V 0 dependences on temperature is not known for SrX, but the present behavior is consistent with available experimental [42] and theoretical [43] …”

Section: Resultssupporting

confidence: 89%

High-pressure and temperature-induced structural, elastic, and thermodynamical properties of strontium chalcogenides

et al. 2016

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Pressure-and temperature-dependent mechanical, elastic, and thermodynamical properties of rock salt to CsCl structures in semiconducting SrX (X = O, S, Se, and Te) chalcogenides are presented based on model interatomic interaction potential with emphasis on charge transfer interactions, covalency effect, and zero point energy effects apart from long-range Coulomb, short-range overlap repulsion extended and van der Waals interactions. The developed potential with non-central forces validates the Cauchy discrepancy among elastic constants. The volume collapse (V P /V 0 ) in terms of compressions in SrX at higher pressure indicates the mechanical stiffening of lattice. The expansion of SrX lattice is inferred from steep increase in V T /V 0 and is attributed to thermal softening of SrX lattice. We also present the results for the temperaturedependent behaviors of hardness, heat capacity, and thermal expansion coefficient. From the Pugh's ratio (/ = B T /G H ), the Poisson's ratio (m) and the Cauchy's pressure (C 12 -C 44 ), we classify SrO as ductile but SrS, SrSe, and SrTe are brittle material. To our knowledge these are the first quantitative theoretical prediction of the pressure and temperature dependence of mechanical stiffening, thermally softening, and brittle nature of SrX (X = O, S, Se, and Te) and still await experimental confirmations.

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Section: Resultssupporting

confidence: 89%

High-pressure and temperature-induced structural, elastic, and thermodynamical properties of strontium chalcogenides

et al. 2016

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“…It was shown that, under a pressure in the range 0-100 GPa, the disper sion of phonon branches changes, the compressibility increases with an increase in temperature, and the specific heat also increases in agreement with the experimental data obtained in [4,5]. The elastic and thermodynamic properties of Li 2 O at high tempera tures in the range 0-1100 K and at high pressures were investigated by Li et al [6] using the ab initio HartreeFock (HF) method in the basis of the linear combina tion of atomic orbitals (LCAO). It was found that the elastic modulus and the Debye temperature decrease monotonically with an increase in temperature.…”

Section: Introductionsupporting

confidence: 53%

“…Debye Grüneisen parameter, which is calculated through the average frequency of vibrations (5) as follows [29,30]: (6) α is the volume thermal expansion coefficient,…”

Section: Computational Techniquementioning

confidence: 99%

Ab initio calculations of the thermodynamic parameters of lithium, sodium, and potassium oxides under pressure

2012

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The parameters of the equation of state and Grüneisen parameters for lithium, sodium, and potas sium oxides have been calculated in the generalized gradient approximation of the density functional theory using a linear combination of atomic orbitals with the CRYSTAL09 software package. The frequencies of long wavelength normal mode vibrations have also been calculated and the dependence of these frequencies on the pressure has been established. The Debye temperature has been determined from the elastic charac teristics of the compounds. The dependences of the Debye temperature, compressibility, thermodynamic potential, entropy, specific heat, thermal expansion coefficient, and thermal conductivity coefficient on the pressure in the range from -3 to -15 GPa and on the temperature have been calculated in the quasi harmonic Debye model. The results obtained are in satisfactory agreement with the available reference and experimen tal data.

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“…It implies that SiC is thermally softened and mechanical stiffened. The normalized volume ( )/ (0) V T V dependence on temperature is not known for SiC, but the present behavior is consistent with available experimental [65] and theoretical [66,67] data on Li 2 O. Figure 22 exhibits the aggregate elastic constants ( ) ij C T with temperature T for SiC.…”

Section: J Adv Ceramsupporting

confidence: 83%

Mechanically induced stiffening, thermally driven softening, and brittle nature of SiC

et al. 2016

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An effective interionic potential calculation with long range Coulomb, charge transfer interaction, covalency effect, short range overlap repulsion extended, van der Waals interaction, and zero point energy effect is implemented to investigate the pressure dependent structural phase transition (ZnS-type (B3) to NaCl-type (B1) structure), and mechanical, elastic, and thermodynamic properties of silicon carbide (SiC). Both charge transfer interaction and covalency effect are important in revealing the pressure induced structural stability, Cauchy discrepancy, anisotropy factor, melting temperature, shear modulus, Young's modulus, and Grüneisen parameter. We also present the results for the temperature dependent behaviors of normalized volume, hardness, heat capacity, and thermal expansion coefficient. SiC is mechanically stiffened and thermally softened as inferred from pressure (temperature) dependent elastic constant's behavior. The Pugh's ratio, the Poisson's ratio , and the Cauchy's pressure C 12 -C 44 for SiC ceramic confirm its brittle nature.

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Ab initio calculations of elastic constants and thermodynamic properties of Li2O for high temperatures and pressures

Cited by 47 publications

References 22 publications

High-pressure and temperature-induced structural, elastic, and thermodynamical properties of strontium chalcogenides

High-pressure and temperature-induced structural, elastic, and thermodynamical properties of strontium chalcogenides

Ab initio calculations of the thermodynamic parameters of lithium, sodium, and potassium oxides under pressure

Mechanically induced stiffening, thermally driven softening, and brittle nature of SiC

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