Properties of ground state for GaN under different external electric fields

Calculations using density functional theoretical (B3PW91) method with 6-311 G (3df, 3pd) basis sets were performed on the total energies, equilibrium structures, dipole moments, atomic charge distributions, infrared intensities, harmonic frequencies, highest occupied molecular orbital (HOMO) energy levels, lowest unoccupied molecular orbital (LUMO) energy levels, and energy gaps of the ground state GaN molecules under different intense electric fields. The results show that the harmonic frequency (f = 576.2218 cm^-1) is close to experiment with data (f = 484.9 cm^-1). With the increase of the external field, the bond length, electric dipole moment, atomic charge distribution, energy gap, infrared intensities, HOMO and LUMO energy are proved to decrease. But harmonic frequencies and total energy are proved to increase. The external electric field has a significant effect on the harmonic frequencies and infrared intensities. These will provide important theoretical reference for the studies of optic properties with materials. (authors)