Band structure cluster complexes

The complex forms purple air-stable crystals and has good solubility in both polar and nonpolar solvents (e.g., acetone, dichloromethane, tetrahydro-furan, benzene, and hexane). It has been characterized crystallographically.7 The structure is an open, but folded, ladder-like array of six metal atoms with the two platinum atoms in the center. The IR spectrum (hexane) exhibits V(co> bands at 2085 (m), 2062 (vs), 2035 (vs), 2016 (w). Pt2Ru4(CO)18 has been found to be very useful for the synthesis of new platinum-ruthenium cluster complexes.10,12,13... 

In the pseudopotential method, core states are omitted from explicit consideration, a plane-wave basis is used, and no shape approximations are made to the potentials. This method works well for complex solids of arbitrary structure (i.e., not necessarily close-packed) so long as an adequate division exists between localized core states and delocalized valence states and the properties to be studied do not depend upon the details of the core electron densities. For materials such as ZnO, and presumably other transition-metal oxides, the 3d orbitals are difficult to accommodate since they are neither completely localized nor delocalized. For example, Chelikowsky (1977) obtained accurate results for the O 2s and O 2p part of the ZnO band structure but treated the Zn 3d orbitals as a core, thus ignoring the Zn 3d participation at the top of the valence region found in MS-SCF-Aa cluster calculations (Tossell, 1977) and, subsequently, in energy-dependent photoemission experiments (Disziulis et al., 1988). 

Silicates make up a large part of the earth s crust, and their physico-chemical properties have obvious importance in geochemistry and mineralogy. Typically structurally complex, they have been mostly studied by very approximate theories with limited predictive power, including small clusters [120]. More recently, band structure studies have begun to reveal some of the secrets of the simpler silicates [121]. In this section we briefly discuss some recent DV cluster studies on annite, a layered iron-bearing silicate which belongs to a class of both natural minerals and synthetic materials of interest as absorbers, carriers, and catalysts [122]. 

Self-consistent Dirac-Slater calculations of molecules and embedded clusters have been recently reviewed by Ellis and Goodman. Relativistic band structure calculations have also been carried out. Dirac scattered-wave calculations have been carried out on a number of inorganic complexes such as W(CO)fi and WjQg - The electronic structure and geometries of X2H2 (X = O,S, Sc and Te) have also been investigated recently. ... 

This is not only important to understand the chemistry of loosely bound complexes but also contributes to elucidating the molecular structure in the transition region between free molecules and solids. One example for this is the formation of clusters in supersonic alkali beams where molecules Na have been observed from x = 2 to x = 12 [10.16]. The spectroscopy of such multimers (clusters) yields dissociation energies, ionization energies, and vibrational structure as a function of the number x of atoms in the cluster. The comparison of these figures with the values in the solid allows the proof of theoretical models, which explain the transition from molecular orbitals to the band structure of solids. 

The relatively broad and featureless absorption spectra of [Fe3S4l clusters belies their complex excited-state electronic structure. This is illustrated in Fig. 5 using P. furiosus 3Fe Fd as an example (42). In addition to the protein band centered at 280 nm, the UV-visible... 

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