Zero-differential overlap Approximation in Cyclic-cluster Model

The extension of INDO and MINDO semiempirical methods to periodic systems has no principal differences compared with the CNDO method. The advantage of these methods is the possibility to make spin-dependent calculations as is done in the UHF method. 

The considered CNDO method for periodic systems formally corresponds to the model of an infinite crystal or its main region consisting of L primitive cells. This semiempirical scheme was also apphed for the cychc-cluster model of a crystal allowing the BZ summation to be removed from the two-electron part of matrix elements. In the next section we consider ZDO methods for the model of a cyclic cluster. 

3 Zero-differential overlap Approximation in Cyclic-cluster Model 

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