Experimental measurements have recently shown that Cu 3SbSe 3 exhibits anomalously low and nearly temperature-independent lattice thermal conductivity, whereas Cu 3SbSe 4 does not exhibit this anomalous behavior. To understand this strong distinction between these two seemingly similar compounds, we perform density functional theory calculations of the vibrational properties of these two semiconductors within the quasiharmonic approximation. We observe strikingly different behavior in the two compounds: almost all the acoustic-mode Grüneisen parameters are negative in Cu 3SbSe 4, whereas almost all are positive in Cu 3SbSe 3 throughout their respective Brillouin zones. The average of the square of the Grüneisen parameter for the acoustic mode in Cu 3SbSe 3 is larger than that of Cu 3SbSe 4, which theoretically confirms that Cu 3SbSe 3 has a stronger lattice anharmonicity than Cu 3SbSe 4. The soft frequency and high Grüneisen parameters in Cu 3SbSe 3 arise from the electrostatic repulsion between the lone s2 pair at Sb sites and the bonding charge in Sb-Se bonds. Using our first-principles- determined longitudinal and transverse acoustic-mode Grüneisen parameters, zone-boundary frequencies, and phonon group velocities, we calculate the lattice thermal conductivity using the Debye-Callaway model. The theoretical thermal conductivity is in good agreement with the experimental measurements.
|Original language||English (US)|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|State||Published - Feb 21 2012|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics