Metastable Frenkel pairs and the W11–W14 electron paramagnetic resonance centers in diamond

Abstract

Diamond is a material that shows great promise for particle detection applications. However, under irradiation with energetic particles, many thermally stable defects are created, made up of lattice vacancies, self-interstitials, and complexes with impurities. Relatively distant Frenkel (vacancy--self-interstitial) pairs have long been used to explain optical and magnetic spectra in irradiated material. However, in diamond we show, using first-principles methods, that the ability of carbon to form $s{p}^{2}$-, $s{p}^{3}$-, and $\ensuremath{\pi}$-bonding configurations leads to particularly strong reconstructions between vacancy--self-interstitial pairs within a few atomic spacings of each other. The resultant complexes are anticipated to be optically and paramagnetically active, and we propose correlation of negatively charged Frenkel pairs with the W11--W14 paramagnetic centers, where substitutional nitrogen donors act as source of electrons and are not an intimate component part of the paramagnetic defects.