First-principles supercell studies of the nitrogen impurity in diamond.

Abstract

We have used a first-principles, local-orbital computational scheme to study the electronic structure of a substitutional N donor impurity in cubic diamond. The calculations were carried out in a supercell framework, using three different supercells with increasing impurity-impurity separation. Comparison of the results from all three supercells allows a reliable extrapolation to the isolated-impurity limit; we find that the N impurity level falls at ${\mathit{E}}_{\mathit{c}}$-0.8 eV, where ${\mathit{E}}_{\mathit{c}}$ is the conduction-band edge. Analysis of the impurity wave function for the three supercells shows that, while the calculated energies indicate a deep donor level, the impurity wave function is nonetheless surprisingly long ranged. The implications of this for the interpretation of recent findings on magnetic multilayers are briefly discussed.