Ab Initio Studies on Silicon Compounds. 2. On the Gauche Structure of the Parent Polysilane

Ab initio crystal orbital calculations are performed on the electronic structures of the parent polysilane. We examine the analysis of the energy band structure and the rotational potential in terms of the trans-gauche conformational transitions. We have found that the trans conformer is the ground state of the polysilane. The gauche-polysilane (GP) is 0.15 kcal/mol per SiH₂ unit above the trans-polysilane (TP). TP has a smaller band gap, lower ionization potential and greater electron delocalization than GP. The effective mass of the hole at the valence band edge is ultimately greater in GP than in TP. All our calculated results suggest that the conservation of near trans conformation is important in the improvement of the semiconductor characteristics of polysilanes.