Ab initio pseudopotential studies of the pressure dependences of structural, electronic and optical properties for GaN

The structural, electronic and optical properties of GaN across its pressure induced phase transformation from the B4 (wurtzite structure) to the B1 (NaCl structure) phase have been studied. The calculations are based on the ab initio plane-wave pseudopotential density functional theory within the generalized gradient approximation for the exchange-correlation potential. The predicted phase transition pressure 45.8 GPa and the optimized lattice constants of B4 GaN under ambient pressure are in very good agreement with experimental and theoretical results. We find that the electronic and optical properties of GaN under high pressure are quite different from those under ambient pressure.