Variation of electronic properties with structure of transition metal trichalcogenides

Electron band structure calculations reveal that ZrSe 3 is a semiconductor with E g approximately 1.5 eV whereas NbSe 3 and TaSe 3 are both highly anisotropic metals. The Peierls transition in NbSe 3 is related to the presence of four quasi-one-dimensional free-electron-like bands crossing the Fermi energy. This feature does not exist in TaSe 3 , and the differences in properties are related to structural differences.