The Thermal Transport, Optical, and Mechanical Properties of 1T-Au6SSe: A First-Principles Study

Abstract

Cluster substitution and constructing Janus materials can independently regulate the physicochemical properties of materials and have been applied in multiple fields. Would it be more effective if both methods are used for simultaneous regulation? In this paper, we obtain monolayer 1T-Au6SSe by replacing the M (M is a transition metal element) atom in monolayer 1T-MS2 with the Au6 clusters and replacing one of the S atoms with the Se atoms. The lattice thermal conductivity (κl) of monolayer 1T-Au6SSe is 0.36 W/mK at 300 K, and its κl is much lower than those of the most monolayer 1T-MS2. This is because, on the one hand, the introduction of Au6 clusters reduces the phonon vibration frequency and softens the phonon mode, resulting in a lower phonon group velocity. On the other hand, the introduction of Se atoms to construct Janus materials makes the crystal structure asymmetrical, and increases the phonon anharmonicity. It is worth noting that the monolayer 1T-Au6SSe as a semiconductor not only has an ideal band gap (1.57 eV) and extremely low κl, but also has excellent optical properties as well as excellent softness. This makes it a promising candidate in the direction of thermal management materials, optoelectronics, and strain engineering.