Molecular dynamics and structure of solids

Abstract

Figure 2. A diagrammatic representation of the variation of the scattering amplitudes of the elements for (i) neutrons and (ii) x rays. The areas of the circles are proportional to the amplitude of the scattered wave: for neutrons the scale of the drawing is ten times larger than for x rays. tinguish, say, rotational disorder from a static disorder which yielded the same overall average distribution of atomic position. J. J. Rush (Na tional Bureau of Standards) : Could you comment on the relative accuracies of electron and neutron diffraction in determining hydrogen positions?G. E. Bacon: It would be reasonable to take a factor of three or four in favor of neutrons. Not only is the visibility of hydrogen relative to other atoms higher for neutrons-say by a factor of two or three in relation to a carbon atom-but also it is very much easier to interpret accurately the measured spectral intensities in terms of the structure amplitude factors of the unit cell. D. T. Goldman (National Bureau of Standards) : Could you comment on how light scattering might fit into this general picture of determination of structure by scattering techniques? G. E. Bacon: I would not expect any detail of the unit cell to be revealed by optical wavelengths, but information on particle size and texture could be forthcoming from samples of suitable transmission or reflectivity.

Measurement of Strontium Monoxide in Methane–Air Flames

“…While diatomic molecules in the gas phase tend to show well-quantized rovibronic fine structure, molecules in condensed phases may not. 18,42 In condensed phases, rotational degrees of freedom are limited by molecular interactions, or rotation is suppressed entirely, causing rotational fine structure to degrade or disappear. Vibrational states, on the other hand, tend to be less affected and often result in only small shifts to the observed vibrational spectra.…”

Triboluminescence and Vapor-Induced Phase Transitions in the Solids of Methyltriphenylphosphonium Tetrahalomanganate(II) Complexes

“…Thus, other factors are involved in the functional attributes of solids in addition to the structure−property relationship. 1,2 The molecular dynamism 6b in the three-dimensional lattices has been demonstrated to affect the physical, 12 chemical, 13 and biological 14 properties of the solid substances. For example, nonluminescent Au(I) complexes 15 of [Au(S 2 CN(C 5 H 11 ) 2 )] 2 series displayed luminescence when they were exposed to acetone, dichloromethane, and chloroform vapors.…”

“…This is because the intermolecular interactions between the solvent vapors and the complex twine the Au•••Au distances 15a,f in crystals. Likewise, the humidity-induced 12,16 structural dynamism has been described to accelerate the rate of multicomponent reactions in the condensed phase. Curiously, relations between the TL emission and the phase transformations have remain unexplored, maybe due to poor understanding of the theories involved.…”

Temperature Mapping in a Model Food Gel using Magnetic Resonance Imaging

“…At constant pressure, as temperature increases, the lattice expands and the barriers in the material are reduced progressively, while at the same time, the activation energy of translational motion increases (enthalpy potential increases) and molecular reorientation is more rapid (Carter and Rush, 1969). Thus, as temperature increases, the self-diffusion coefficient increases.…”