The influence of pressure on high-pressure, high - temperature annealing of type Ia diamond

摘要

The influence of temperature and pressure conditions during high-pressure, high-temperature (HPHT) annealing on the dissociation of nitrogen aggregates is investigated, and special attention is paid to the influence of pressure. When PT conditions are above the diamond-graphite equilibrium line, an activation energy of 5.6 +- 1.4 eV is calculated from the Arrhenius plot of the dissociation rate of A centres by assuming that the dissociation reaction of A centres follows first order kinetics. A second estimate for the binding energy of the A centres, derived from the equilibrium concentrations of A centres and C centres at three different temperatures, gives a value of 7.66 +- 0.6 eV. The dissociation rate of A centres is enhanced by a factor of approx 10 when the PT point during the HPHT annealing is located in the graphite stable region of the carbon phase diagram.