Effects of the Vacancy Point-Defect on Electronic Structure and Optical Properties of Diamond under High Pressure

By ultra-soft pseudo-potential approach of the plane wave based on the density-functional theory, the electronic structures and optical properties of diamond without and with vacancy point-defects were calculated at 255 GPa. The calculated results show that: at a shock pressure of 255 GPa, shock-induced vacancy point-defects in diamond crystal cause defective states within the band gap, and the optical absorption induced by the vacancy point-defects appears in the visible-light region of ~390-570 nm, and there is the transparency loss of diamond in that region. However, in the visible-light region of ~570-780 nm diamond remains transparent (its optical-absorption coefficient is still zero). Effects of shock-induced vacancy-defects on reflectivity and loss-function spectrums are similar: main-spectral peak move slightly toward short-wave region, and their intensity decreases to a small degree.