Theoretical Descriptions of the Electronic Structure

The theoretical treatments for both optical and tunneling experiments on Q Ds require, first, a calculation of the level structure. Various approaches have been developed to treat this problem, including effective mass-based models, with various degrees of band-mixing effects [50, 52, 54,73], and a more atomistic approach based on pseudopotentials ]69, 74]. Both approaches have been successfully applied to various nanocrystal systems [55, 56, 74—77]. In order to model the PLE data, it is necessary to calculate the oscillator strength of possible transitions, and to take into account the 

In another approach, Niquet et ol. modeled the junction parameters (capacitances and tunneling rates), and used a tight-binding model for the level structure [80,81], 

4 Atomic-Like States in Core-Shell Nanocrystals Spectroscopy and Imaging 

IIZ V a (ML) shells with nominal core radii -1.7 nm. The spectra were offset 

In this case, the p state was red-shifted upon increasing shell thickness, whereas the s level did not shift, but yielded a closure of the CB s-p gap. 

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The theoretical description of the electronic structure has been obtained by means of the LAPW method on an ab-initio basis1101. The electronic potential is determined self-consistently for the elementary cell of the bare host structure, which consists of 44 atoms. More complicated systems, where the tubes are filled with water molecules are also taken into account. Recent self-consistent full-potential calculations (FLAPW) are performed to refine the results 11 . 

The stereochemistry and functions of all iron porphyrin-containing proteins can be attributed to the varied electronic structure of iron for the oxidation and spin states that are stable in physiological environments. Theoretical descriptions of the electronic structure of iron should be, in principle, applicable to the understanding of structure-function relationships in hemeproteins. 

There are now good theoretical descriptions of the electronic structures contributing to the optical absorption bands in spectra of porphyrin radicals and ferryl species [160,167] most charge-transfer bands in the latter are due to a transition from a porphyrin p orbital to an Fe-0 tt orbital [167], However, in the absence of a prior knowledge of the structure around the Felv site (and/or spectra of a variety of synthetic model compounds) it is not straightforward to assign an optical spectrum to a ferryl species. Thus the intermediate assumed to be the ferryl species in the binuclear haem c /Cub centre of cytochrome c oxidase [168] has a spectrum at 580 nm essentially identical [169] to that of low-spin ferric haem a3 compounds (e.g. cyanide). 

Energy and charge transport in saturated and conjugated polymeric solids represent limiting cases in the applicability of the precepts of band theoretical descriptions of the electronic structure of solids. Discussions of the nature of intrinsic localized electronic states and their consequences to treatments of transport phenomena in such materials comprise an important section of these proceedings. 

Often the most important properties of materials are directly or indirectly connected to the presence of defects and in particular of point defects [18]. These centers determine the optical, electronic and transport properties of the material and usually dominate the chemistry of its surface. A detailed understanding and a control at atomistic level of the nature (and concentration) of point defects in oxides is therefore of fundamental importance to synthesize new materials with well defined properties. This has lead in recent years to the birth of the new field of defect engineering. Of course, before to be created in controlled conditions point defects have to be known in all aspects of their physico-chemical properties. The accurate theoretical description of the electronic structure of point defects in oxides is essential for the understanding of their structure-properties relationship. 

Shortly after the initial discovery of doping and the metal-insulator transition in polyacetylene, a theoretical description of the electronic structure was... 

Ab initio MO calculations for the potential curves of H2S+ and HzO+ have been carried out208 in order to obtain a theoretical description of the electronic structure and geometry of these systems. The results are in satisfactory agreement with experiment, and show that both radicals are very similar, both in geometry and in electronic structure. 

THEORETICAL DESCRIPTIONS OF THE ELECTRONIC STRUCTURES OF THE CARBONYL HALIDES... 

Brown CA, Pavlosky MA et al (1995) Spectroscopic and theoretical description of the electronic structure of S = 3/2 iron-nitrosyl complexes and their relation to O2 activation by non-heme iron enzyme active sites. J Am Chem Soc 117 715-732... 

ESIPT process have used either semi-empirical or simple ah initio methods (see for instance [18-27]). Only recently significant progress in the theoretical description of the electronic structure of excited states of larger polyatomic systems has been made [28,29], which has allowed a more quantitative ab initio treatment of the excited-state PE surfaces relevant for this process [30-37]. In the following we discuss the more important conclusions concerning ESIPT reactions which emerge from these studies. 

Valence bond theory gave the earliest theoretical description of the electronic structure of a complex. According to this theory, a complex forms when douhly occupied ligand orbitals overlap unoccupied orbitals of the metal atom. 

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