Theory of the structures of non-crystalline solids

Abstract

-The study of the structures and properties of non-crystalline solids and their interrelationships is a rapidly growing field of research, involving interdisciplinary efforts at the frontiers of chemistry, solid state physics, and materials science. These materials differ from the better-understood crystalline solids by the lack of long range three-dimensional translational periodicity in their atomic arrangements.Consequently, this study cannot make use of the simplification attendant with the use of repetitions of a small unit cell. We present a review of the state-of-the-art in the theoretical study of the structures of such non-crystalline solids. The topics covered include structural models, the nature of order and disorder, model systems of low dimensionality, chemical bonding considerations, thermodynamic and kinetic considerations, dynamic simulations, elastic and vibrational properties, electronic structure and properties, amorphous metals and alloys, silica glasses and related alloys, liquids and superlattices. It is our hope that this review will generate more interest among chemists in the scientific and technological problems and challenges presented by these materials.

Incipient low-temperature formation of MAX phase in Cr–Al–C films

“…As it is known, long-range-order (LRO) defines ordered (crystalline) structures while short-range-order (SRO) defines disordered structures. Loss of LRO causes the appearance of disorder in the solid state by mainly two mechanisms [32]: (1) thermodynamic disordering that leads to occurrence of the amorphous phase, characterized (among other models) by the "random close packed" model; (2) kinetic disordering (a continuous disordering process) that leads to occurrence of nanocrystalline materials, solid solutions or glassy states (as in bulk metallic glasses), characterized by the "continuous random network" model. Of most importance is the fact that kinetic disordering preserves the local crystalline symmetry into the glassy state, at a range defined by the SRO.…”

Effect of antimony addition on the thermal and electrical-switching behavior of bulk Se–Te glasses

“…According to the empirical correlation proposed [32][33], the glass-transition temperature T g is known to be linearly dependent on the optical band gap E g and hri, by the relation:…”

“…where, b is a linear proportionality constant for each value of hri, and E 04 is a measure of the optical gap E g and the energies of the weakest bonds in the alloy [33].…”

Emergent Properties in Locally Ordered Molecular Materials

“…Organic materials can exist in crystalline, semicrystalline, amorphous, or self-assembled structures, resulting in different local ordering. [21,61] To examine how different orderings can affect the local dielectric response, we oriented sparse (1 molecule per nm 2 ) benzene monolayers such that the benzene molecules were either oriented parallel (along the p system) or perpendicular (perpendicular to the p system) to the applied electric field, as shown in Figure 3a. Figure 3a depicts the local dielectric response (on the x axis) as a function of probe position (on the y axis).…”