Electronic thermal conductivity as derived by density functional theory

Article

关键词: TEMPERATURE THERMOELECTRIC PROPERTIES;    TOTAL-ENERGY CALCULATIONS;    SUPERLATTICE STRUCTURES;    PHONON-GLASS;    HIGH FIGURE;    EFFICIENCY;    DEVICES;    MERIT;   

DOI  :  10.1103/PhysRevB.88.045134

来源: SCIE

【 摘 要 】

Reliable evaluation of the lattice thermal conductivity is of importance for optimizing the figure of merit of thermoelectric materials. Traditionally, when deriving the phonon mediated thermal conductivity kappa(ph) = kappa - kappa(el) from the measured total thermal conductivity kappa the constant Lorenz number L-0 of the Wiedemann-Franz law kappa(el) = TL0 sigma is chosen. The present study demonstrates that this procedure is not reliable when the Seebeck coefficient vertical bar S vertical bar becomes large which is exactly the case for a thermoelectric material of interest. Another approximation using L-0 - S-2, which seems to work better for medium values of S-2 also fails when S-2 becomes large, as is the case when the system becomes semiconducting/insulating. For a reliable estimation of kappa(el), it is proposed that a full first-principles calculation by combining density functional theory with Boltzmann's transport theory has to be made. For the present study such an approach was chosen for investigating the clathrate type-I compound Ba8Au6-xGe40+x for a series of dopings or compositions x. For a doping of 0.8 electrons corresponding to x = 0.27 the calculated temperature dependent Seebeck coefficient agrees well with recent experiments corroborating the validity of the density functional theory approach.

【 授权许可】

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