A quantum-chemical open-shell method was used to construct a large model unit cell for the [Si–V]0 impurity complex. It was shown that the ground spin-triplet state of the complex exerted a tunnel (rather than Jahn–Teller) splitting that was associated with an off-center shift of the Si atom along the trigonal axis of the fully symmetrical atomic configuration, D3d. This complex (a source of electron spin resonance KUL1, S = 1) appeared to be the optical 1.68eV center, with a typical (≈ 0.001eV) splitting of the zero-phonon line. Intracenter optical excitation occurred from the filled orbital doublet, localized at Si, to the orbital doublet localized at 3 of six C atoms which neighbored Si and had a multiplet structure.

Electronic Structure of Neutral Silicon – Vacancy Complex in Diamond. S.S.Moliver: Technical Physics, 2003, 48[11], 1449-53