Pressure dependence of the optical-absorption edge of diamond

The effect of hydrostatic pressure on the optical-absorption edge of type-IIa diamond has been measured at room temperature to 2.3 GPa using a sapphire anvil cell. The absorption edge shifts toward higher energy at a rate of 6.0 meV/GPa, in fair agreement with the first-principles calculations of Fahy et al. [Phys. Rev. B 35, 5856 (1986); 36, 3373 (1987)].