Fixed-node diffusion quantum Monte Carlo calculations were made of the ground and excited state energetics of the neutral vacancy defect. Its multiplet structure was modeled by using guiding wave functions of Slater-Jastrow type, with symmetrized multi-determinant Slater parts. For the ground state, the 1E state was in agreement with experiment. The calculated energy of the lowest dipole allowed transition was consistent with the experimentally observed GR1 band, which had been attributed to the neutral vacancy, but no previous ab initio calculations of this transition had been made. The calculated multiplet splitting of over 2eV indicated the importance of properly treating electron exchange and correlation in the system. Diffusion quantum Monte Carlo calculations were made of the formation and migration energies of the vacancy defect.

Quantum Monte Carlo Study of the Optical and Diffusive Properties of the Vacancy Defect in Diamond. R.Q.Hood, P.R.C.Kent, R.J.Needs, P.R.Briddon: Physical Review Letters, 2003, 91[7], 076403 (3pp)