Electronic properties, stability, and lattice thermal conductivity of bulk Janus 3R-PtXY (X, Y=S, Se, Te) transition-metal dichalcogenide

In this work, we investigate the electronic properties and dynamical stability of bulk Janus PtSSe, PtSTe, and PtSeTe belonging to the 3R polymorph and compared them to 1T phase through first-principles calculations. 3R-PtSTe and 3R-PtSeTe are semimetals, whereas 3R-PtSSe exhibits a semiconductor nature with a small indirect bandgap of 0.147 eV, while for the 1T phase, all structures are semimetals. To elucidate the stability of these structures, we calculated the phonon spectrum and found that all structures were dynamically stable. Furthermore, free energy calculations showed that monolayer PtXY favors the 1T polytype up to T = 357, 370, and 298 K for PtSSe, PtSTe, and PtSeTe, respectively, and for higher temperatures, the 3R phase is more favorable. Through inspection, the bulk 3R-PtXY is seen to have smaller lattice thermal conductivity than the corresponding 1T-PtXY, which is beneficial for thermoelectric applications. Our results can be served as a benchmark for future experimental and theoretical research on these materials