Electronic structures and state densities for faujasite clusters

MINDO/3 and CNDO/2 methods have been applied to clusters simulating the structure of faujasite, with the inclusion of from 6 to 12 aluminum-oxygen and silicon-oxygen tetrahedra. A study has been made of how the integral and orbital electron-state densities vary with the dimensions of the zeolite fragment, the boundary conditions, and the calculation method. The fine structure in the cation state density peaks for aluminum in the valency band is only slightly dependent on the boundary conditions and the cluster dimensions, while the differences between the MINDO/3 and CNDO/2 results amount to a systematic shift in the peaks together with slight changes in the fine structure. On the other hand, the boundary conditions have a considerable effect on the orbital state density profiles for the oxygen ions in the upper valency quasiband for the faujasite clusters.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 22, No. 2, pp. 210–216, March–April, 1986.