Ultralow and Anisotropic Thermal Conductivity in Semiconductor As2Se3

• Main Authors: González-Romero, Robert L, Antonelli, Alex, Chaves, Anderson S, Meléndez, Juan J
• Format: Journal Article
• Language: English
• Published: 15-12-2017
• Subjects: Physics - Materials Science
• DOI: 10.48550/arxiv.1710.02299

An ultralow lattice thermal conductivity of 0.14 W$\cdot$ m$^{-1} \cdot$
K$^{-1}$ along the $\vec b$ axis of As$_2$Se$_3$ single crystals was obtained
at 300 K by first-principles calculations involving the density functional
theory and the resolution of the Boltzmann transport equation. This ultralow
lattice thermal conductivity arises from the combination of two mechanisms: 1)
a cascade-like fall of the low-lying optical modes, which results in avoided
crossings of these with the acoustic modes, low sound velocities and increased
scattering rates of the acoustic phonons; and 2) the repulsion between the
lone-pair electrons of the As cations and the valence $p$ orbitals of the Se
anions, which leads to an increase in the anharmonicity of the bonds. The
physical origins of these mechanisms lie on the nature of the chemical bonding
in the material and its strong anisotropy. These results, whose validity has
been addressed by comparison with SnSe, for which excellent agreement between
the theoretical predictions and the experiments is achieved, point out that
As$_2$Se$_3$ could exhibit improved thermoelectric properties.