"First-principles Investigation of the Type II Al-Substituted Ternary and Quaternary Clathrate Semiconductors R8Al8Si128 (R = Cs, Rb) and Cs8Na16Al24Si112"

Dong Xue, Charles Myles

Research output: Contribution to journalArticle

Abstract

Structural and vibrational properties of the aluminium-substituted ternary and quaternary clathrates R8Al8Si128 (R = Cs, Rb), Cs8Na16Al24Si112 are investigated. The equilibrium volume of R8Si136 expands when all Si atoms at the 8a crystallographic sites are replaced by Al. Formation of the Al–Si bond is thus anticipated to correlate with decreased guest vibration modes. Underestimation of the predicted lattice phonon conductivity kL (1.15Wm1 K1) compared to a previous experiment (1.9Wm1 K1) in Cs8Na16Si136 is thought to arise from our evaluation on the phonon mean free path l using the “scattering centers” model. Accordingly, we expect that the “three-phonon” processes dominate the determination of the phonon relaxation time, leading to a more reasonable in the R8Al8Si128 system. Additionally, the “avoided-crossing” effect causes no appreciable difference in the sound speed for acoustic phonons in this framework. Starting with configuration optimization about aluminium arrangements in
Original languageEnglish
Pages (from-to)125-137
JournalApplied Sciences
StatePublished - Jan 1 2019

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