Symmetry lowering through surface engineering and improved thermoelectric properties in Janus MXenes
Himanshu Murari, Subhradip Ghosh
Abstract
(M = Ti, Zr, Hf and M' = Mo, Zr, Hf; M ≠ M'). Our calculations show that the thermoelectric figure-of-merit can be improved significantly by such surface engineering. We discuss in detail, both qualitatively and quantitatively, the origin behind high thermoelectric parameters for these compounds. Our in-depth analysis shows that the modifications in the electronic band structures and degree of anharmonicity driven by the dispersions in the bond strengths due to the lowering of symmetry, an artefact of surface engineering, are the factors behind the trends in the thermoelectric parameters of the MXenes considered. The results also substantiate that the compositional flexibility offered by the MXene family of compounds can generate a complex interplay of symmetry, electronic structure, bond strength and anharmonicity which can be exploited to engineer thermoelectric materials with improved properties.