Dong CHEN
金属学报(英文版)
The structural and thermoelasticity of antifluorite magnesium silicide at high temperatures were studied by using the plane-wave pseudo-potential method in the framework of density functional theory. The bulk ground-state quantities such as lattice constants, cell volumes, band structures and elastic constants were calculated. It showed that the elastic constants of Mg2Si were well consistent with the experimental data under ambient conditions. The crystal cell volume and bulk modulus of Mg2Si as functions of applied temperature were also presented. The lattice dynamics was applied to determine the phonon dispersion curves. To complete the fundamental characterisation of this crystal, the coefficients of thermal expansion (CTE), isochoric heat capacities and Debye temperature of Mg2Si in the whole temperature range from 0 K to 1300 K and pressure range from 0 GPa to 7.48 GPa were investigated. The results were in favourable agreement with the previous theoretical calculations and the existing experimental data.
关键词:
Mg2Si
Dong CHEN
,
Jingdong CHEN
,
Yinglu ZHAO
,
Benhai YU
,
Chunlei WANG
,
Deheng SHI
金属学报(英文版)
doi:10.1016/S1006-7191(08)60082-4
The equilibrium lattice parameter, relative volume V/V0, elastic constants Cij, and bulk modulus of titanium nitride are successfully obtained using the ab~initio plane-wave pseudopotential (PW-PP) method within the framework of density functional theory. The quasi-harmonic Debye model, using a set of total energy vs molar volume obtained with the PW-PP method, is applied to the study of the elastic properties and vibrational effects. We analyze the relationship between the bulk modulus and temperature up to 2000 K and obtain the relationship between bulk modulus B and pressure at different temperatures. It is found that the bulk modulus B increases monotonously with increasing pressure and decreases with increasing temperature. Moreover, the Debye temperature is determined from the non-equilibrium Gibbs functions.
关键词:
Elastic constants
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null
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null
Dong CHEN
,
Jingdong CHEN
,
Yinglu ZHAO
,
Hailiang HUO
,
Benhai YU
,
Deheng SHI
金属学报(英文版)
doi:10.1016/S1006-7191(08)60106-4
The crystal and electronic structures of LaNi4.75Sn0.25 intermetallics and LaNi4.5Sn0.5Hy (y=2.0, 2.5) intermediate phase have been investigated by the full-potential linearized augmented plane wave (FP-LAPW) method. Hydrogen occupation sites in LaNi4.5Sn0.5Hy have been determined based on Westlake$'$s criterions: (1) the minimum hole radius is 0.04~nm; (2) the minimum H-H distance is 0.21~nm; as well as geometry optimizations and internal coordinates optimizations. We find that hydrogen atoms prefer to occupy the 12n*, 6m, 12o, 6m* sites in LaNi4.5Sn0.5H2.0 and the 6m*, 4h, 6m, 12o, 12n* sites in LaNi4.5Sn0.5H2.5. The specific coordinates of hydrogen atoms in LaNi4.5Sn0.5Hy are also determined. The results show that hydrogen atoms tend to keep away from tin atoms. The maximum hydrogen content decreases compared with LaNi5. The interactions between Sn and Ni with H play a dominate role in the stability of LaNi4.5Sn0.5-H system. Lattice expansion and increment of Fermi energy E F show that both Sn and H atoms decrease structural stability of these alloys.
关键词:
Rare-earth intermetallics
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