Silicon-interstitials-based Benchmarking of DFT Exchange-correlation Potentials

Diffusion Monte Carlo (DMC) benchmarks DFT functionals: LDA, GGA, and HSE [1]. Extensive DFT studies on single-, di-, and tri-interstitials [2] provide stable structures and converged energies. For single-interstitial formation energies, our DMC results confirm earlier work [3], with 1.5 and 1.0 eV underpredictions for LDA and GGA, respectively. We continue to observe this trend in most di- and tri-interstitials. Additionally, we find HSE reproduces DMC results for single-interstitals. Preliminary analysis indicates that large LDA and GGA discrepancies with DMC occur for highly distorted defect configurations. \begin{itemize} \item[{[1]}] J.~Heyd \emph{et al.}, J.Chem.Phys. \textbf{118}, 8207 (2003). \item[{[2]}] D.~A.~Richie \emph{et al.}, Phys. Rev. Lett. \textbf{92}, 45501 (2004). \item[{[3]}] W.~-K.~Leung \emph{et al.}, Phys. Rev. Lett. \textbf{83}, 2351 (1999). \end{itemize}