Theory prediction of the electronic structure, mechanical and thermodynamic properties of Ca₅Pd₆Ge₆ under pressure

ABSTRACT

The electronic structures, mechanical and thermodynamic properties of Ca₅Pd₆Ge₆ under pressure have been investigated via the first-principles calculations. The optimised lattice constant was in good agreement with the experimental data. Resulting from the Ca-3d, Ge-4p and Pd-4d states contribution, at the Fermi level, the Ca₅Pd₆Ge₆ exhibits metallic behaviour. The elastic constants were calculated, and the result implies that Ca₅Pd₆Ge₆ was mechanically stable below 50 GPa. The polycrystalline modulus increases almost linearly with pressure. The B/G ratio indicated that Ca₅Pd₆Ge₆ was brittle, and the brittle to ductile transition occurs at 2.5 GPa. Furthermore, the Debye temperature θ_D, the minimum thermal conductivity K was obtained. Finally, the isochoric heat capacity C_v and entropy S were evaluated by the quasi-harmonic Debye model in consideration for the temperature effect.

GRAPHICAL ABSTRACT

KEYWORDS:

• Intermetallic
• first-principles calculations
• the quasi-harmonic Debye model
• mechanical behaviours
• thermodynamic properties

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The authors thank the project of innovative talents of North China University of Water Resources and Electric Power (grant number 70483) and the program for innovative research team (in science and technology) in University of Henan Province (grant number 16IRTSTHN017) for financial support.