Solid-state problems

There have been a number of improvements in techniques, and more convenient models have been formulated however, the basic approach of the pseudopotential total energy method has not changed. This general approach or standard modd is applicable to a broad spectrum of solid state problems and materials when the dec-trons are not too localized. Highly correlated electronic materials require more attention, and this is an area of active current research. However, considering the extent of the accomplishments and die range of applications (see Table 14.3) to solids, dusters, and molecules, this approach has had a major impact on condensed matter physics and stands as one of the pillars of the fidd. 

Waugh and his group (410-414), Stoll et al. (415), and Alla and Lippmaa (416) were the first to apply the technique to solid-state problems. Good reviews of the technique have been prepared by Freeman and Morris (417), Benn and Gunther (418) and Mehring (10), the latter being particularly relevant to the topics discussed in this review. 

Before the discovery, in 1986, by Bednorz and Muller [1] of high-Tc superconductivity, there was a rather widespread belief that Solid State Theory was satisfactorily built so as to allow the comprehension of any solid state problem, provided the computations to be carried out were feasible. Nourishing this believe there was, on the free quasi-particle side, the Fermi Liquid Theory and tools as Green Functions and Diagrammatic Perturbation Theory, which allowed to study most of the band-theoretic-based solid-state properties. Namely, Diagrammatic Perturbation Theory has... 

A rigorous attack of many solid-state problems requires a command of physics that cannot be expected of the reader of the present text. The picture presented in this chapter is thus fragmentary and, in some cases, greatly simplified. 

I. B. Bersuker, The Jahn-Teller Effect As a General Tool for Solving Molecular and Solid State Problems Novel Findings. J. Mol. Struct. 2007, 838, 44-52. 

Pisani, C. (1987). Hartree-Fock ab initio approaches to the solution of some solid-state problems state of the art and prospects. Int. Rev. Phys. Chem. 6, 367-84. 

Normally, in solid-state problems a harmonic approximation is used enabling one to introduce normal coordinates for the intermolecular subsystem. The density matrix in these coordinates equals the product of the density matrices of independent oscillators, the expressions for which are well-known [158],... 

Hence, just as in the solid-state problem, one would also expect the following effects to occur [48] in a ferrofluid for a large direct-current bias field superimposed on which is a small alternating-current field ... 

There are several cogent reasons to include a chapter on the solid state in a treatise devoted to chemical hardness, and other concepts, derived from density functional theory. One is that DFT has been the theoretical method of choice in dealing with solid-state problems for a number of years. 

Due to the large flexibility of hydrogen molecules in the solid hydrogen, it was decided, contrary to the normal use of cluster models in solid state problems, to optimize the clusters fully, e.g. not to use the crystal parameters from X-ray or similar experiments. 

The rest of this section is organized as follows a fairly straightforward account of modern Marcus theory is given in Section III,A which emphasizes the distinction between electron and nuclear tunneling. The superexchange mechanism and other QE theories are considered in Section III,B, and the analogy between them and certain solid state problems are considered. It is worth reemphasizing that. 

Rudolph Mossbauer discovered the phenomenon of recoil-free nuclear resonance fluorescence in 1957-58 and the first indications of hyperfine interactions in a chemical compound were obtained by Kistner and Sunyar in 1960. From these beginnings the technique of Mbssbauer spectroscopy rapidly emerged and the astonishing versatility of this new technique soon led to its extensive application to a wide variety of chemical and solid-state problems. This book reviews the results obtained by MSssbauer spectroscopy during the past ten years in the belief that this will provide a firm basis for the continued development and application of the technique to new problems in the future. 

Almost all quadrupolar nuclei in the Periodic Table have been studied experimentally in one or more of their compounds. A current list 0f these results is available in a database published by the JAICI (Japan Association for International Chemical Information, Tokyo, Japan). Biennial International Symposia on nuclear quadrupole interactions are also excellent sources of the latest experimental and theoretical works. As an illustration of the kind of solid-state problems that may be studied, we give some recent examples of such investigations. Sensitivity. or signal-to-noise ratio (SNR) in WQR spectroscopy, as well as NMR, depends on the observed frequency, which in turn, depends, inter alia, on the value of Q. The lighter elements tend to have low values of Q and low NQR frequencies and low sensitivities. for example, a... 

In this chapter we apply the dimensional scaling method to a model solid state problem, namely three-dimensional lattices of hydrogen a-toms. In the pressure regimes where such lattices are stable, they are also predicted to be metallic, so we will refer to them by the term metallic hydrogen. The primary goal of this chapter is to outline some basic techniques which will be required for dimensional scaling treatments of electronic structure in extended systems, but we will also look at some specific results for metallic hydrogen. 

The increasing interest in NMR spectroscopy of what in some conferences in this field is commonly termed "other nuclei" is unmistakable. Chemists and biologists who employ NMR spectroscopy to study their problems have, however, been somewhat reluctant to study nuclei with electric quadrupole moments. These nuclei frequently give rise to broad NMR signals, sometimes too broad to be detectable with ordinary high resolution NMR spectrometers. Spectrometers that could cope with broad NMR signals of low intensity, "wide-line" spectrometers, have been available since the mid 1950 s but it appears that most of these instruments ended up in physical laboratories where the research was primarily directed towards solid state problems. 

---