Density functional electronic structures calculations of GeSe2

Valence and conduction band electronic structures for amorphous and crystalline GeSe2 are discussed based on the density functional calculation of the density of states for model clusters. Results are compared with photoemission and inverse photoemission spectra and their peak structures are reproduced very well. We present a full interpretation of these spectra through investigations of partial density of states and molecular orbitals around the bandgap, and reveal that the states around the bandgap are Se 4p lone-pair states and Ge-Se anti-bonding states, and the split band structure of the higher conduction band is made up of the anti-bonding states correspond to the bonding states in the split valence band. The higher conduction band is also revealed to be combined with effects of 4d orbitals and inter-layer interactions. (C) 2001 Elsevier Science B.V. All rights reserved.