Adsorption and diffusion of an alkali-metal adatom on transition-metal dichalcogenides

Abstract

Employing total-energy density-functional theory calculations the adsorption energies, the diffusion pathways, and the barriers for a Li adatom on stepped ${\mathrm{TiSe}}_{2}$ surfaces with full relaxation of the atomic environment were studied. The minimum-energy paths for Li diffusion on a ${\mathrm{TiSe}}_{2}$ (0001) surface and across the $(10\overline{1}0)$ and $(\overline{1}2\overline{1}1)$ steps have been calculated. At the $(\overline{1}2\overline{1}1)$ step edge an Ehrlich-Schwoebel barrier of $0.31\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ was obtained, which is additional to the diffusion barrier of $0.25\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ on the flat surface. The energies for subsequent diffusion within the van der Waals gap have been calculated, too.