Oxyanions tetrahedral, electronic structure

There is widespread interest (220) in the electronic structures of tetrahedral oxyanions of the type M04. Being quasi-isoelectronic the neutral tetroxides, M04, M = Ru, Os, are well suited for vapor-phase UPS studies (49, 102, 140) of the bonding in this type of system. Unfortunately impurities are apparent in two of these spectral studies (102, 140), and in one of them (140) doubts have been raised (49) about the validity of the reported vibrational fine structure. Furthermore, the interpretations presented in the three papers are somewhat different. Overall, the interpretation of Orchard et al. (49) appears to be the most reasonable. 

Following a short review of early studies of the valence band of tetrahedral oxyanions of types X04" some recent results of this field are discussed. High resolution XPS measurements of the valence band of phosphorus and sulphur oxyanions made possible a rigorous test of various theoretical models. For DV-Xa cluster MO calculations, experimentally determined crystal structure information were used to set up realistic model clusters. In the case of the S04 cluster, the results of several model calculations ab initio, DV-Xa, hybrid models) are presented. From the comparison of these results a better understanding of the role of the contributions from different effects to the MO one-electron energies can be obtained. 

The electronic structure of tetrahedral oxyanions and their derivatives has been extensively studied by many authors during the past decades. The earlier attempts were summarized by Prins [1]. Since the work of Walsh [2] and that of Wolfsberg and Helmholz [3] several semi-empirical theoretical studies have been published [4-7]. Later ab initio [8-10] and scattered wave calculations [11] have been also reported. Among the experimental investigations, Prins mentioned the electron spin resonance measurements of radicals formed by ejection or addition of an electron from or to certain oxyanions, obtaining information on just those molecular orbitals which contained unpaired electrons. [12] X-ray absorption and emission studies provided usefial information on a limited number of molecular orbitals in the valence band [13-19]... 

Silicon dioxide. Theoretical calculations of the electronic structures of the SiOi 38,639 GeO tetrahedral oxyanions have been carried out... 

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