The aggregation of N defects in synthetic diamond was simulated by using a Monte Carlo technique. The model reproduced experimental data for the case where no transition metal defects were present in the diamond and the aggregation obeyed second-order kinetics. When Ni impurities were included, they released interstitials which enhanced the mobility of the N and so accelerated the rate of aggregation. An assumed barrier to the formation of N pairs from N interstitial/substitutional pair complexes was necessary in order to reproduce the observed aggregation rates. At 1500C, N aggregated around the Ni and significant concentrations of Ni–N complexes were observed.

The Kinetics of the Capture of Nitrogen by Nickel Defects in Diamond. A.Smith, A.Mainwood, M.Watkins: Diamond and Related Materials, 2002, 11[3-6], 312-5