Solid state terminology

Conjugated polymers are generally poor conductors unless they have been doped (oxidized or reduced) to generate mobile charge carriers. This can be explained by the schematic band diagrams shown in Fig. I.23 Polymerization causes the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the monomer to split into n and n bands. In solid-state terminology these are the valence and conduction bands, respectively. In the neutral forms shown in Structures 1-4, the valence band is filled, the conduction band is empty, and the band gap (Eg) is typically 2-3 eV.24 There is therefore little intrinsic conductivity. 

Table 3.4 Connection between molecular and solid state terminologies...

By an electron jump, we have formed an electron-hole pair, to use the solid-state terminology. This can occur in two ways the two atoms can be widely separated, or they can be adjacent. In the first case, the energy required is less, by just the coulombic energy of a neighboring Na and Cl , or 5.1 eV. This means that the electron and the (positive) hole attract each other by this amount. 

TABLE 13.1. Approximate Analogs Between Molecular and Solid-State Terminology... 

So, by the 1990s, Professor Rao had been active in several of the major aspects which, together, were beginning to define materials chemistry crystal defects, phase transitions, novel methods of synthesis. Yet, although he has been president of the Materials Research Society of India, he does not call himself a materials chemist but remains a famous solid-state chemist. As with many new conceptual categories, use of the new terminology has developed sluggishly. 

The interfaces between a semiconductor and another semiconductor (e.g. the very important pin junction, the interface between p- and ft-type semiconductors), between a semiconductor and a metal (the Schottky barrier) and between a semiconductor and an electrolyte are the subject of solid-state physics, using a nomenclature different from electrochemical terminology. 

These ideas developed by chemists resemble the bipolaron model, which presents the solid-state physicist s view of the electronic properties of doped conducting polymers [96]. The model was originally constructed to characterize defects in inorganic solids. In chemical terminology, bipolarons are equivalent to diionic states of a system (S = 0) after oxidation or reduction from the neutral state. The transition from the neutral state to the bipolaron takes place via the polaron state (= monoion, S = 1/2,... 

The engineering principles of thermodynamics, kinetics, and transport phenomena, as well as the chemistry and physics of molecnlar strncture, serve as the basis for the remaining topics in this book. In this chapter, we look at what for many applications is the primary materials selection criterion mechanical properties. As in the previous chapter, we focns primarily on the properties of materials, bnt discnss briefly the mechanics, both in the fluid and solid states, that give rise to the properties. There is a great deal of new terminology in this chapter, and it is cumnlative—take time to nnderstand all the definitions before proceeding to the next section. 

In order to find the domain of LCVD, it is necessary to compare various vacuum deposition processes chemical vapor deposition (CVD), physical vapor deposition (PVD), plasma chemical vapor deposition (PCVD), plasma-assisted CVD (PACVD), plasma-enhanced CVD (PECVD), and plasma polymerization (PP). All of these terms refer to methods or processes that yield the deposition of materials in a thin-film form in vacuum. There is no clear definition for these terms that can be used to separate processes that are represented by these terminologies. All involve the starting material in vapor phase and the product in the solid state. 

To end this section, it may be useful to the reader to give a table collecting some analogies between molecular and solid state theory (Table 3.4). The table is taken from Albright et al. (1985), and is useful in connecting quantum theorist terminology to that of solid state physicists. 

Temperature exerts a strong influence on the rates of most solid state reactions. In theoretical discussions of the temperature dependencies of rates of reactions involving solids, the terminology developed for homogeneous rate processes has often been used without explicit modification to describe heterogeneous processes. 

An essentially identical experiment has also been referred to as Homonuclear Hartmann-Hahn spectroscopy [50,51] or HOHAHA (the two differ only in some technical details in the originally published sequences). This name arises from its similarity with methods used in solid-state NMR spectroscopy for the transfer of polarisation from proton to carbon nuclei (so-called crosspolarisation), which are based on the Hartmann-Hahn match described below. For the same reason, the transfer of magnetisation during the TOCSY sequence is sometimes referred to as homonuclear cross-polarisation. Throughout this text the original TOCSY terminology is used, although TOCSY and HOHAHA are now used synonymously in the chemical literature. 

O. Delgardo-Friedrichs and M. O Keeffe, Crystal nets as graphs terminology and definitions. J. Solid State Chemistry, 178, 2480-2485 (2005). 

Before examining these electronic effects, we should delve a little more deeply into the theory and terminology of solid state chemistry than was done on pages 269-272. Specifically, if there is an infinite array of identical orbitals (say H lx) represented by d> . , , 3. . . related by translational symmetry and spaced at distance a. then we can have linear combinations,... 

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