A new model to calculate electronic states of the diamond vacancies was developed by using many body techniques. This model was based on physical assumptions of previous molecular models but does not use configuration interaction. The present model permitted an accurate and unified treatment to be made of electronic levels and related eigen functions for diamond vacancies, in addition to transition energies of the first dipole-allowed transitions in the neutral (V0) and negatively charged (V−) vacancies, GR1 and ND1 band. Their optical transition intensities were calculated for the first time. In order to obtain these results, a generalized form of the Hubbard Hamiltonian was solved which consisted of all electron–electron interaction terms on an atomic orbital basis. The spatial symmetry of the defect, of Td symmetry, was incorporated in the form of the Hamiltonian and the eigenstates automatically had the correct spin and symmetry properties. The possibility of reducing the wide gap between theoretical and semi-empirical data, by including deformation of the dangling orbital or delocalization of the vacancy electrons to the next-nearest neighbor atoms of the vacancies, was considered. The prediction of the low-lying 3T1 level of the neutral vacancy in diamond was consistent with experimental expectations. molecular mechanics

Details of a Theoretical Model for Electronic Structure of the Diamond Vacancies. M.H.Saani, M.A.Vesaghi, K.Esfarjani, A.Shafiekhani: Diamond and Related Materials, 2004, 13[11-12], 2125-30