New 111-type Semiconductor ReGaSi Follows 14e- Rules

Electron-counting rules were applied to understand the stability, structural preference, and physical properties of metal disilicides. Following predictions made by 14 electron counting rules, the ordered semiconductor ReGaSi, the first ternary phase in this system, is proposed and successfully synthesized. It crystallizes with a primitive tetragonal structure (space group P4/nmm) closely related to that of MoSi2-type ReSi2, but with Ga and Si orderly distributed in the unit cell. The band structure, density of states, and crystal orbital calculations confirm the electron count hypothesis to predict new stable compounds. Calculations, based on 14 electrons per ReGaSi units, show a small indirect band gap of ~0.2 eV around Fermi level between full and empty electronic states. Additionally, first-principles calculations confirm the site preference of Ga and Si which is observed through the structural refinement. Experimental magnetic measurements verified the predicted non-magnetic properties of ReGaSi.