抄録
By following straightforwardly the model originally proposed by Phillips and Van Vechten and revised afterwards by Kleinman for explaining the nonlinear optical constants of zinc-blende type semiconductors, without their important but invalid assumption ⟨a|ξ|a⟩+⟨b|ξ|b⟩=0, we have proved that their model is essentially equivalent to the primitive LCHO–MO model and the combination parameter λ and the overlapping integral S in the latter model are related with the two parameters Eh and C, the homopolar and heteropolar energy gaps, in the former model, in a simple form λ={(Eg+Eh)\sqrt1−S+C\sqrt1+S}⁄{(Eg+Eh)\sqrt1−S−C\sqrt1+S}. Observed values of the SHG constant χ123(2) of several semiconductors are compared with the calculated values by introducing the reduction factor 2/3 on the heteropolar energy gap C.
