Theory of boron aggregates in diamond: First-principles calculations

It is well known that nitrogen forms aggregates in diamond. However, little is known regarding aggregation of boron, an impurity that can be incorporated in very high concentrations. In this paper we present the results of first-principles calculations regarding the structure and properties of boron-aggregates, and simple complexes with native defects. We find that certain complexes are shallower acceptors than Bₛ, and that pairs of boron interstitials, suggested as having a role in the recently observed low-temperature superconduction in B-doped diamond, are unstable and do not provide the shallow acceptor states required.