Identification of the pressure-induced phase transition of ZnSe with the positron annihilation method

This paper studies the pressure-induced phase transition between zincblende (B3) and NaCl (B1) structure ZnSe by using the hydrostatic pressure first-principles pseudopotential plane wave method. The energy-volume and enthalpy-pressure curves are employed to estimate the transition pressure. It is found that ZnSe undergoes a first-order phase transition from the B3 structure to the B1 structure at approximately 15 GPa derived from the energy-volume relation and 14 GPa based on deduction from enthalpy-pressure data. The pressure-related positron bulk lifetimes of the two ZnSe structures are calculated with the atomic superposition approximation method. In comparison with the 13.4% reduction in volume of ZnSe at the transition pressure, the positron bulk lifetime decreases more significantly and the relative value declines up to 22.3%. The results show that positron annihilation is an effective technique to identify and characterize the first-order phase transition and can give valuable information about changes in micro-scale, such as volume shrinkage and compressibility.