By using the irreducible representation basis functions of the point group whose symmetry is lower than Td, a decomposition of the total density of states is considered. The calculation-results are obtained for the D3d point group in Si. Combining with the Koster-Slater Green's function method and on site approximation, the calculation results are used to analyse the electronic structures of the divacancy and the chalcogenide paris (S20, Se20, Te20) in Si. Some interesting results are obtained as follows; The distribution of the local spectral densities closely related to the deep states in forbidden band is similar for point and pair defects. Under the expellant action caused by the local spectral density, the symmetrical A10s (chalcogenide pairs) and Eg, (divacancy) states are higher than the antisymmetrical A2us (chalcogenide pairs) and Eu, (divacancy) states. The distribution of the deep state wavefuctions in Bloch space is also, similar for point and pair defects.
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