Examination of Lone s

The ternary compound CuSbSe2 exhibits lower lattice thermal conductivity, relative to its analogous counterpart Cu3SbSe4. Such anomaly is attributed to the presence of lone s2 pair electrons in CuSbSe2. In this work, the proposed lone pair effects are carefully examined by first-principles calculations combined with Wannier-orbital analysis. It is revealed that the Sb atom exhibits the similar electron configuration both in Cu3SbSe4 and CuSbSe2. Moreover, the Wannier-function calculations indicated that the Sb-5s orbital is strongly distorted in CuSbSe2, rather than in Cu3SbSe4. These observations are just in contradiction to the explanation of the lone s2 pairs. Based on the reasonable reproducing of experimental lattice thermal conductivity, the calculations and analysis disclose that the anomalous low thermal conductivity of CuSbSe2 is due to the reduced p-p bonding strength between Sb and Se, originating in the structural distortion.