Structural and electronic properties of diamond with hypothetical vacancies stabilized by nitrogen or boron atoms

In an effort to understand the behavior of hard materials in the presence of vacancies or impurities, we study the structural and electronic properties of diamond with specified vacancies. In our model, five carbon atoms in the shape of a centered tetrahedron are missing and 12 carbon atoms surrounding the vacancy are replaced by nitrogen or boron atoms. The bulk modulus of the material with nitrogen substitution is greater than that without substitution around vacancy, although it is still slightly smaller than that of vacancy-free diamond. Boron substitution results in a substantial relaxation of atomic positions and a large reduction in bulk modulus. Born’s criterion for mechanical stability is satisfied in both cases. The calculated electronic structures suggest that the doping of N atoms around the vacancy as modeled here fails to generate conduction electrons while that of B atoms successfully produces conducting holes. @S0163-1829~97!02324-2#