Infrared absorption in amorphous selenium Original Research Article

The infrared (IR) absorption spectrum of amorphous selenium (a-Se) are calculated for the atomic structure constructed by a molecular dynamics with recently proposed chain model using an semiempirical electronic structure calculation. Its microscopic mechanism is investigated with an IR formula for chains in terms of bond and induced current correlations. The stretching band in the IR spectrum has two peaks, which are related to the intermediate range order that dihedral angle sequences with the signs of (+,−,+,−) and (−,+,−,+) hardly occur due to steric hindrance. The result urges us to modify the conventional picture that a-Se consists of the polymer chains with completely random sequences of the signs of the dihedral angles.