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

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 from 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 sp²-, sp³- and π-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.