Cluster model, spectroscopic data

Studies of larger species are more complex and the difficulty in the evaluation of their potential surfaces increases with their size. Up to now accurate potentials have been obtained by inversion of spectroscopic data or through high level ab initio calculations " for several triatomic vdW systems. Thus, the interactions for such clusters are available with satisfactory accuracy, which permits the testing of various models of nonadditivity for their ability to reproduce a number of experimental observations. These facts made complexes composed of two rare-gas atoms and a dihalogen molecule especially attractive targets for the study of nonadditive forces. The first attempt to extract information on nonadditive interactions from... 

Ca2+ depletion has been shown to change the binding affinity of Mn, to modulate the exchange coupling within the Mn cluster and to mediate photooxidation of the Mn ions (see reference 431).Based on the spin-projection model for clusters with localized spins coupled by two-centre spin-exchange interaction468 possible structural models have been evaluated as candidates for the OEC. Three model were found to satisfy the constraints of the EPR and most other spectroscopic data, furthermore possible locations of Ca2+ were proposed (for a thorough discussion see reference 431). 

The results of the testing of the dimensional theory for homonuclear clusters, Xn (n 7). Indicates a general agreement with the model. Unfortunately an accurate and meaningful comparison of the data on clusters larger than trlmers Is severely limited by the lack of accurate experimental spectroscopic data. The uncertainties Involved In the standard estimation procedures are... 

A new empirical potential for water has been developed using spectroscopic data, which is able to model condensed water with good accuracy.483 The potential is referred to as the VRT(ASP-W)III potential (the third fitting of the Anisotropic Site Potential with Woemer dispersion to Vibration-Rotation Tunnelling data). It give excellent results for vibrational properties of water clusters up to (H20)6, but unlike earlier spectroscopically derived potentials also models the liquid state well. MC simulations are used to study the liquid state properties. It is noted that this potential only partly accounts for many-body interactions (the induction term) and the simulations do not include... 

All of the spectroscopic data can be understood within a CuOa( > cluster model, which is valid when the U s are large relative to the bandwidths (S S), i.e. when correlation effects dominate covalent or hybridization effects. Both La and CuO contain CuOt groups (10), having 4 short and 2 long Cu-0 bonds. The 123 HTSC contains CuOs and planar CuOd groups (10). The different n may alter the relative intensities of various features as pointed out below, but similar features are present in each case. The different bond lengths may increase the widths of the spectral features, but little else since correlation dominates. 

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