Self-trapped Exciton Radiation Spectrum And V <sub> At Nh <sub> 4 </ Sub> Cl And Nh <sub> 4 </ Sub> Br Crystal K </ Sub> The Heart Of The Absorption Spectrum

On the basis of one-electron Hartree-Fock approximation, the extended-ion method has been used to investigate luminescence energies of the Self-Trapped Exciton(STE) and absorption energies of the Vk-center in NH4Cl and NH4Br crystals , The energy and the corresponding equilibrium configuration of the crystal is determined by minimizing the total energy of the system, which is composed of the Coulomb energy, the repulsive energy, the defect electron energy, the polarization energy and the CNDO cluster energy. The electron is represented by a linear combination of floating Is gaussians. We use a hybrid pseudopotential method to determine the energy and states of the defect electron. The electron wavefunction and lattice relaxation are determined in a self-consistent way. The results show that the luminescence energies of the STE and the absorption energies of the Vk-center are in good agreement with the experimental results.