A density functional theory study of models for the N3 and OK1 EPR centres in diamond.

The defects observed in natural and synthetic diamonds provide a fingerprint of their differing growth conditions, as well as the thermal and mechanical processes they have experienced. Of the first row elements it is perhaps surprising that little evidence exists for oxygen in the form of distributed point-defects. Paramagnetic centres labelled N3 and OK1 have been assigned to two structural arrangements of pairs of substitutional nitrogen and oxygen, but there is no direct evidence for the involvement of the oxygen. In this paper we present the results of density functional simulations of N-O pairs in diamond, and review them in light of the experimental evidence. We also present analysis for other structures proposed in the literature (Ti-N, Ti-V-N, NV(2) and NVO), and show that none are particularly plausible.

Density functional studies of muonium in nitrogen aggregate containing diamond: the Mu(X) centre.

Diamond has potential as a wide band-gap semiconductor with high intrinsic carrier mobility, thermal conductivity and hardness. Hydrogen is involved in electrically active defects in chemical vapour deposited diamond, and muonium, via muon spin spectroscopy, can provide useful characterization for the configurations adopted by H atoms in a crystalline material. We present the results of a computational investigation into the structure of the Mu(X) centre proposed to be associated with nitrogen aggregates. We find that the propensity of hydrogen or muonium to chemically react with the lattice makes the correlation of Mu(X) with nitrogen aggregates problematic, and suggest alternative structures.