Coupled polaron-phonon effects on Seebeck coefficient and lattice conductivity of B13C2 from first principles

Title
Coupled polaron-phonon effects on Seebeck coefficient and lattice conductivity of B13C2 from first principles
Authors
김형철매서드 카비아니
Keywords
Seebeck coefficient; Lattice conductivity; Lattice dynamics; Density functional theory; Boron carbides; Polaron; Phonon
Issue Date
2013-04
Publisher
Physical review B, Condensed matter and materials physics
Citation
VOL 87, NO 15, 155133-1-155133-6
Abstract
The anomalous temperature-independent behavior of the Seebeck coefficient and the lattice thermal conductivity of B13C2 are explained through polaron and phonon evolutions found using ab initio molecular dynamics (AIMD). Analyses of lattice dynamics show that the unique icosahedron structures dominate the optical phonon modes and CBC intericosahedral bonds dominate the local acoustic vibration. We identify that the temperature-induced Jahn-Teller distortion and electron-phonon coupling in icosahedron structures create small polarons (i.e., charge trapping and phonon softening). We also verify that large-displacement chain atoms scatter heat-conducting phonons. Using equilibrium and nonequilibrium AIMD methods (including entropy and energy analyses), we predict the Seebeck coefficient and its components as well as the lattice thermal conductivity, and we find good agreement with experiments. Softened and localized phonons make a significant vibrational contribution to the Seebeck coefficient and allow for an amorphous-like lattice thermal conductivity.
URI
http://pubs.kist.re.kr/handle/201004/45718
ISSN
10980121
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KIST Publication > Article
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