Cubic scaling algorithm for the random phase approximation: applications to defects

Aktivität: VorträgeVortragAndere

Beschreibung

The random phase approximation (RPA) to the correlation energy is among the most promising methods to obtain accurate correlation energy differences from diagrammatic perturbation theory at modest computational cost. The calculations are, however, usually one to two orders of magnitude more demanding than conventional density functional theory calculations. Here, we show that a cubic system size scaling can be readily obtained, which reduces the computation time by one to two orders of magnitude for large systems. Furthermore, the scaling with respect to the number of k points used to sample the Brillouin zone can be reduced to linear order. In combination, this allows accurate and very well-converged single-point RPA calculations, with a time complexity that is roughly on par or better than for self-consistent Hartree-Fock and hybrid-functional calculations [1]. The present implementation enables new applications. Here, we apply the RPA to determine the energy difference between diamond Si and β-tin Si, the energetics of the Si self-interstitial defect and the Si vacancy, the latter with up to 256 atom supercells. We show that the RPA predicts Si interstitial and vacancy energies in excellent agreement with experiment and diffusion Monte Carlo results. Si selfinterstitial diffusion barriers are also in good agreement with experiment, as opposed to previous calculations based on hybrid functionals or range-separated RPA variants [2]. The talk will also cover a critical discussion of the limitations of the RPA and possibly improvements of the RPA, as well, as of errors introduced by the pseudopotential or related projector augmented wave approximation [3]. [1] Merzuk Kaltak, Jiří Klimeš, and Georg Kresse, J. Chem. Theory Comput., 10, 2498–2507 (2014). [2] Merzuk Kaltak, Jiří Klimeš, and Georg Kresse, Phys. Rev. B 90, 054115 (2014). [3] Jiří Klimeš, Merzuk Kaltak, and Georg Kresse, Phys. Rev. B 90, 075125 (2014)
Zeitraum28 Apr. 2015
EreignistitelThe Quantum Mechanics of Defects - Nothingisperfect
VeranstaltungstypKonferenz
OrtAscona, SchweizAuf Karte anzeigen