Comparison of screened hybrid density functional theory to diffusion Monte Carlo in calculations of total energies of silicon phases and defects

Nearly quantitative agreement between density functional theory (DFT) and diffusion Monte Carlo (DMC) calculations is shown for the prediction of defect properties using the Heyd-Scuseria-Ernzerhof (HSE) screened-exchange hybrid functional. The HSE functional enables accurate computations on complex systems, such as defects, where traditional DFT may be inadequate and DMC calculation computationally unfeasible. The screened-exchange hybrid functional retains the benefits of earlier hybrid functionals in terms of treating strongly correlated insulators but unlike them it can be applied to metallic phases. This study concentrates on the DFT energetic predictions of point defects in silicon and on phase energy differences between the diamond and metallic beta-tin phases.