Structurally disordered solids are characterized by their lack of spatial order that is evidenced by the great variety of ordered solids. The former class of materials is commonly termed amorphous or glassy, the latter crystalline. However, both classes share, many of the other physical properties of solids, e. g. , me chanical stability, resistance to shear stress, etc. The traditional macroscopic distinction between the crystalline and the glassy states is that while the former has a fixed melting point, the latter does not. However, with the availability and production of a large number of materials in both crystalline and amorphous states, and their easy inter-convertability, simple de finitions are not possible or at best imprecise. For the present purpose, it is sufficient to say that in contrast to the crystalline state, in which the posi tions of atoms are fixed into adefinite structure, ex cept for small thermal vibrations, the amorphous state of the same material displays varying degrees of de parture from this fixed structure. The amorphous state almost always shows no long range order. Short range order, up to several neighbors, may often be retained, although averaged considerably around their crystalline values. It is generally believed that the amorphous state is a metastable one with respect to the crystal line ordered state, and the conversion to the crystal line state may or may not be easy depending on the na ture of the material, e. g.

Inhalt
Formation and Transformation Behavior of Amorphous Solids.- On the Structure Analysis of Amorphous Materials.- On the Structure of Amorphous Films.- Structural Modelling of Disordered Semiconductors.- Some Theorems Relating to the Structure of Amorphous Solids.- Polymorphs.- Optical Properties of Tetrahedrally Bonded Amorphous Semiconductors: Absorption Spectra and Absorption Edge.- Photoluminescence.- to Photoemission.- Photoemission of Disordered Elemental Semiconductors.- Mathematical Methods for Calculating the Electron Spectrum.- Some Theorems Relating to Densities of States.- Theory of Optical Absorption of Disordered Solids.- Comments on the Theory of Localized States in Semiconducting Noncrystalline Solids.- Transport Properties of Amorphous Semiconductors.- Electrical Transport in Semiconducting Noncrystalline Solids.- Inelastic Coherent Neutron Scattering in Amorphous Solids.- Infrared and Raman Spectroscopy of Amorphous Semiconductors.- Dynamics of Structurally Disordered Solids.- Phonons in Amorphous Solids.- Local Order and Low Frequency Modes in Amorphous Solids: Magnetic Resonance Techniques.- Bonding in Non-Tetrahedrally Coordinated Amorphous Solids.- Light Scattering in Liquid Semiconductors.- Author Index.