Half-electron model, definition

In this chapter, we will consider the other half of a model chemistry definition the theoretical method used to model the molecular system. This chapter will serve as an introductory survey of the major classes of electronic structure calculations. The examples and exercises will compare the strengths and weaknesses of various specific methods in more detail. The final section of the chapter considers the CPU, memory and disk resource requirements of the various methods. 

Let us consider a MV dimer — d" in which for the sake of definiteness we assume that n < 4 (less than half-filled d-shells). The main features of the phenomenon can be understood in the framework of the classical spin model [77]. As distinguished from a quantum spin, a classical spin represents the infinite spin limit for which all the directions in the space are allowed. From the classical point of view, for Hund s configuration of the ion the extra electron lines up its spin, Sg, parallel to the spin sq of the d" ion (spin core). In the classical limit, 1/2, so that max 2 0 and 0. These two extremes correspond to parallel and antiparal-... 

Further standard voltages could be measured and placed into an electrochemical sequence with other pairs of half-cells, as can be found in many chemistry teaching books. The extent of the introduction of the hydrogen half-cell as a standard electrode can be determined in each individual lesson. If one consequently describes all redox reactions in relation to the metal sequence, redox or electrochemical sequence with ions and offers the students model drawings (see Figs. 8.3 and 8.4), then the electron transfer and the redox definition, in terms of involved smallest particles, becomes even clearer and the mixing at the language level of substances and that of particles can be effectively suppressed. 

---