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Several inconsistencies contained in a paper (1969) by Van Vechten on interband energy calculation of covalent solids are discussed. In particular it is shown that energy gaps corresponding to E0, E1 and E2 can not be fitted to an expression of type Eg2 = Eh2 + C2, whether there is a d-core or not.
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K. S. Song (1974) studied this question.
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