Electronic structure models

Part 2, Model Chemistries, provides an in-depth examination of the accuracy, scope of applicability and other characteristics and trade-offs of all of the major well-defined electronic structure models. It also gives some general recommendations for selecting the best model for investigating a particular problem. 

Electronic structural model. The size selective reactivity of these metal clusters Ts surprisi ng. Certainly the metal cluster are... 

We have undertaken a gas phase photodissociation study of Mo2 2 H3 4 whose results are viewed in light of the one electron electronic structure models available for this compound... 

Gaussian 98M , available in 2002, is an implementation of the Gaussian 98 electronic structure modeling program for the Mac OS X environment. It models a broad range of molecular systems under a variety of conditions, and performs its computations starting from the basic laws of quantum mechanics. 

In the following Sections we analyse the previously listed classes of QC methods of electronic structure modelling in terms of the density matrices. 

The implementation of the scattering approach and of some simphfied electronic structure models for describing the transport behavior of short poly(dG)-poly(dC) DNA wires [14] have been recently independently proposed within two main classes of models. One involves dephasing [123-125] and the other involves the hybridization of the r-stack [122]. 

Trindle, C. Shillady, D. Electronic Structure Modelling. Connections Between Theory and Software" CRC Press Boca Raton, FL, 2008. 

All the linear and nonlinear optical properties introduced above are therefore expressed in terms of linear, quadratic and cubic response functions. They can be computed with high efficiency using analytical response theory [9] with a variety of electronic structure models [8],... 

The free energies of the initial (i) and final (f) states, the so-called diabatic states in the ET process (discussed in more detail in Section 3.54, Reaction Field Hamiltonian, Electronic Structure models), are given by [28]... 

These spectroscopic data have collectively been used to evaluate the results of DFT calculations on the related electronic structure model MoO(edt)2 in both the +5 and +6 oxidation states (106). It is important to note that the calculations... 

In this chapter the electronic-structure model developed for extended main-group systems describes properties that do not depend on the surface states. It is simply... 

Coupling of quantum mechanical molecular subsystems with larger classically treated subsystems has traditionally involved electronic structure models describing molecules embedded in a dielectric medium and this is a research area that has expanded tremendously over the last three decades [2-36]. Most of this work has involved electronic structure methods that have been based on uncorrelated electronic structure methods [2-12,15-19]. Accurate description of the electronic structure of molecular systems requires that the correlated electronic motion in the molecule is incorporated and therefore a number of correlated electronic structure methods have been developed such as the second order Moller-Plesset (MP2) [28,30,90,91], the multiconfigurational self-consistent reaction field (MCSCRF) [13,20] and the coupled-cluster self-consistent reaction field (CCSCRF) method [36]. 

Sr2FeMo06- While this material has been known since 1963, intense interest was sparked by the announcement of room temperature MR in 1998. The material is ferro or ferrimagnetic with Tc > 400 K and a metallic conductor, Figure 35. This unusual combination of properties can be explained in terms of the half-metallic ferromagnetic electronic structure model. Figure 36. Note that the Fermi... 

Fig. 6.17. Electronic structure models for FeS (a) molecular-orbital energy levels for the FeSj" octahedral cluster calculated using the MS-SCF-Za method, for low-spin Fe + (singlet, as in pyrite) and high-spin Fe + (quintet) states (after Tos-sell, 1977) (b) electron structure model for pyrrhotite based on calculated energy levels for the FeSe " cluster (from Tossell, 1977) and sulfur Ai(3 emission and K absorption spectra (Diagram after Sakkopoulos et ah, 1984) (c) schematic energy-level diagram for the troilite form of FeS (after Goodenough, 1967).

Fig. 6.26. An electronic structure model for covellite (CuS), based on calculations using the MS-SCF-Aa method. Discrete energy levels are shown for the clusters...

In this, the last major chapter of the book, we turn our attention to the applications of modern electronic structure models and eoncepts to more general geochemical problems namely, those described by Goldschmidt as being eoncerned with the distribution of elements in the geochemical spheres and the laws governing the distribution of the elements (see Preface). 

Detailed LEED studies of ZnS (and other zincblende-structure compounds, including ZnTe and CdTe) have established that the (110) surface is reconstructed by movement of the Zn atoms inward (towards the bulk solid) and of the S atoms outward. Displacements of the cation and anion in the uppermost layer by <<0.5 A and in the second layer by 0.1 A compared to the bulk are involved (Duke, 1983). Harrison (1976, 1980) has explained this in terms of an electronic structure model by conversion of half-occupied dangling-bond hybrid orbitals at both Zn and S on the... 

It has recently been pointed out by R0nne et al. [344] that the structure and dynamics of liquid water constitute a central theme in contemporary natural science [345-353]. Modem theoretical considerations are aimed at (a) a detailed description of an electronic structure model of hydrogen bonding, applied to water molecules (see, e.g., Ref. 354), (b) models that involve a certain critical temperature where the thermodynamic response functions of water diverge (see, e.g., Ref. 353), and (c) models that presuppose a coexistence between two liquid phases [344] a low-density liquid phase at the low-pressure side and a high-density liquid phase at the high-pressure side (see also Refs. 355-357). 

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