Electronic energy chemical system

Firstly, the power of molecular graphics to improve our chemical understanding and to derive qualitative structure property relation(QSPR) will be described. Molecular graphics is also useful for visual representation of the geometry of chemical systems during energy minimization and molecular dynamics calculations. 3-d representation of the results of quantum chemical calculations such as MO contour, electron density and electrostatic potential are effective ways of getting chemical information from the pile of numbers. 

We have specifically mentioned free energy, because under the prevailing isothermal conditions only this is useful energy which is not dissipated. In isothermal chemical systems, free energy is exchanged by the transformation of electronic energy such as present in chemical bonds. In photo- and radio-... 

In this chapter we shall first outline the basic concepts of the various mechanisms for energy redistribution, followed by a very brief overview of collisional intennoleciilar energy transfer in chemical reaction systems. The main part of this chapter deals with true intramolecular energy transfer in polyatomic molecules, which is a topic of particular current importance. Stress is placed on basic ideas and concepts. It is not the aim of this chapter to review in detail the vast literature on this topic we refer to some of the key reviews and books [U, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, and 32] and the literature cited therein. These cover a variety of aspects of tire topic and fiirther, more detailed references will be given tliroiighoiit this review. We should mention here the energy transfer processes, which are of fiindamental importance but are beyond the scope of this review, such as electronic energy transfer by mechanisms of the Forster type [33, 34] and related processes. 

The species H2 and H3+ are important as model systems for chemical bonding theory. The hydrogen molecule ion H2+ comprises 2 protons and 1 electron and is extremely unstable even in a low-pressure gas discharge system the energy of dissociation and the intemuclear distance (with the corresponding values for H2 in parentheses) are ... 

Some methods of describing electron correlation are compared from the point of view of requirements for theoretical chemical models. The perturbation approach originally introduced by Mpller and Plesset, terminated at finite order, is found to satisfy most of these requirements. It is size consistent, that is applicable to an ensemble of isolated systems in an additive manner. On the other hand, it does not provide an upper bound for the electronic energy. ... 

Potential energy hypersurfaces form the basis for the complete description of a reacting chemical system, if they are throughly researched (see also part 2.2). Due to the fact that when the potential energy surface is known and therefore the geometrical and electronical structure of the educts, activated complexes, reactive intermediates, if available, as well as the products, are also known, the characterizations described in parts 3.1 and 3.2 can be carried out in theory. 

---