Atomic solids properties

The engineering of novel deviees requires, in many eases, materials with finely seleeted and preestablished properties. In partieular, one of the most promising lines of synthetic materials research consists in the development of nanostructured systems (nanocomposites). This term describes materials with structures on typical length scale of 1-100 nm. Nanometric pieces of materials are in an intermediate position between the atom and the solid, displaying electronic, chemical and structural properties that are distinct from the bulk. The use of nanoparticles as a material component widens enormously the available attributes that can be realised in practice, which otherwise would be limited to bulk solid properties. 

One of the first attempts to calculate the thermodynamic properties of an atomic solid assumed that the solid consists of an array of spheres occupying the lattice points in the crystal. Each atom is rattling around in a hole at the lattice site. Adding energy (usually as heat) increases the motion of the atom, giving it more kinetic energy. The heat capacity, which we know is a measure of the ability of the solid to absorb this heat, varies with temperature and with the substance.8 Figure 10.11, for example, shows how the heat capacity Cy.m for the atomic solids Ag and C(diamond) vary with temperature.dd ee The heat capacity starts at a value of zero at zero Kelvin, then increases rapidly with temperature, and levels out at a value of 3R (24.94 J-K -mol-1). The... 

Chapter 10, the last chapter in this volume, presents the principles and applications of statistical thermodynamics. This chapter, which relates the macroscopic thermodynamic variables to molecular properties, serves as a capstone to the discussion of thermodynamics presented in this volume. It is a most satisfying exercise to calculate the thermodynamic properties of relatively simple gaseous systems where the calculation is often more accurate than the experimental measurement. Useful results can also be obtained for simple atomic solids from the Debye theory. While computer calculations are rapidly approaching the level of sophistication necessary to perform computations of... 

In contrast to low-energy electrons, X-rays are very weakly scattered by atoms, a property which leads to the success of X-ray diffraction as a means of determining the structure of bulk solids through scattering from atoms over a large depth into the... 

A general theoretical approach to monolayer physical adsorption is discussed. In this theory, the isotherms and heats of adsorption at given T are given as functions of the interaction energies of the adsorbed atoms with the solid and with each other. The general equations reduce to localized and mobile adsorption when the potential variations over the surface are either very large or very small. Intermediate cases are also included. Gas atom-solid interaction energy functions are computed from the known pair interaction potentials for several rare gas systems, and it is shown that a considerable amount of information can be obtained about the adsorption properties of such systems from these potential functions. 

To the extent that the electronic structure is describable in terms of independent atoms, the properties of inert-gas solids are easily understandable and not so interesting. There are, however, one or two points that should be made. The optical absorption spectra of isolated atoms consists of sharp lines that correspond to transitions of the atom to excited slates, and to a continuous spectrum of absorption beginning at the ionization energy and continuing to higher energy. The experimental absorption spectra of inert-gas solids (Baldini, 1962) also show fairly sharp lines corresponding to transitions from the valence p states to excited s... 

Crystalline solids can be classified into five categories based on the types of particles they contain atomic solids, molecular solids, covalent network solids, ionic solids, and metallic solids. Table 13-4 summarizes the general characteristics of each category and provides examples. The only atomic solids are noble gases. Their properties reflect the weak dispersion forces between the atoms. 

T.A. Keith, in C.F. Matta, R.J. Boyd (Eds.), Atomic Response Properties, in Quantum Theory of Atoms In Molecules From Solid State to DNA and Drug Design edn., Wiley-VCH, Weinheim, 2007, pp. 61-94 (chapter 3). 

The properties of atomic solids vary greatly because of the different ways in which the fundamental particles, the atoms, can interact with each other. For example, the solids of the Group 8 elements have very low melting (freezing) points (see Table 14.2), because these atoms, having filled valence orbitals, cannot form covalent bonds with each other. So the forces in these solids are the relatively weak London dispersion forces. 

Metals represent another type of atomic solid. Metals have familiar physical properties they can be pulled into wires, they can be hammered into sheets, and they are efficient conductors of heat and electricity. However, although the shapes of most pure metals can be changed relatively easily, metals are also durable and have high melting points. These facts indicate that it is difficult to separate metal atoms but relatively easy to slide them past each other. In other words, the bonding in most metals is strong but nondirectional. 

Perhaps the most important consideration when discussing the development and use of empirical potentials for studying atomic solids is that pairwise potential models are often not very suitable The performance of pairwise potential models can be bad for transition metals and even worse for semiconductors There are a number of reasons why this is so, many of which are due to the fundamental behaviour of pairwise potentials for certain experimental properties. The most oft-quoted properties are as follows ... 

Classical molecular dynamics (MD) simulations are a useful tool for elucidating the interplay between the molecular structure, solids properties, and interface-molecule interactions in determining the heat transport properties of nanometer systems [37,38]. Moreover, MD simulations were extensively used for testing the applicability of the Fourier s law in low dimensional systems [2] and for suggesting molecular level machines [29,30]. In standard-classical MD studies, one essentially disregards the electronic degrees of freedom, and considers an all-atom force-field for the atomic coordinates, with dynamics ruled by Newtonian equations of motion. 

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