The application of an atomic effective potential to the electronic structure and bonding of Si2

Abstract

A series of computations has been carried out on the ground (³Σ⁻_g) and first excited state (¹Σ⁺_g) of Si₂(R=4.244 a₀) both with and without the use of an atomic effective or pseudopotential. A Gaussian double‐zeta basis set was utilized and partial electronic correlation was introduced into the wave function by means of the generalized valence bond (GVB) approximation. In all cases, the all electron and effective potential computations are in good agreement. The computations indicate that the stability of the ground (³Σ⁻_g) state is due to the tendency of silicon to prefer the divalent s²p² atomic configuration rather than the tetrahedral sp³ atomic configuration. In contrast to the C₂ carbon analog, the first excited (¹Σ⁺_g) state of Si₂ is shown to possess a relatively weak π bond.