THEORY OF IMPURITIES IN DIAMOND

Recent theoretical investigations into the structure and properties of two major impurities in diamond are reviewed. Particular attention is placed on nitrogen (N), the dominant impurity in natural type I diamond. It is shown how calculations of the structure, electronic and vibrational properties of nitrogen-containing defects have shed light on a variety of experimental information gathered in the last 50 years. Problems considered include nitrogen as an isolated impurity, in the A and B centres (complexes believed to contain two and four nitrogen atoms, respectively) and in the platelet defects which may contain thousands of N atoms. Finally, the present understanding of hydrogen, a major impurity in type II diamond, is reviewed.