Structurally Induced Semimetal-to-Semiconductor Transition in1T-TiSe2

We show that observed changes in the nature of the conducting state of $1T$-Ti${\mathrm{Se}}_2$ in going from the normal semimetallic state to the charge-density-wave semiconducting state can be successfully modeled by variation of a single structural parameter, $z$, which modulates the Ti-Se bond length. These ab initio band-structure results lead to a number of interesting experimental consequences.