Structural and electronic properties of type I and VIII Sr₈Ga₁₆Sn₃₀ clathrates under compression

Abstract

Based on the ab initio density functional theory under generalised gradient approximation, we calculated the total energy and band structure for the type I and VIII Sr₈Ga₁₆Sn₃₀ under hydrostatic pressure, the results reveal that the type VIII Sr₈Ga₁₆Sn₃₀ is the stable phase and the type I Sr₈Ga₁₆Sn₃₀ is the metastable phase, and there is no phase transformation between the type I and VIII Sr₈Ga₁₆Sn₃₀ under hydrostatic pressure. The type I and VIII Sr₈Ga₁₆Sn₃₀ are indirect semiconductors with band gaps of 0.125 and 0.009 eV respectively. With increasing pressure, the band gaps are increased, and there is no significant change for the dispersion of band near the Fermi lever. The stability of Sr₈Ga₁₆Sn₃₀ is lower than that of Ba₈Ga₁₆Sn₃₀; therefore, it is more difficult in the synthesis of Sr₈Ga₁₆Sn₃₀ compared to that of Ba₈Ga₁₆Sn₃₀.

Keywords:

• Thermoelectric materials
• Electronic properties
• Sr₈Ga₁₆Sn₃₀
• First principles calculation