Crystal structures relaxation program

Implementation of atomic multipoles in a crystal structure relaxation program... 

This formalism has been used to adapt THBREL, a crystal structure relaxation program which has been widely used in modelling inorganic solids, to model rigid molecules whose electrostatic interactions are described by a DMA model (Willock et al., 1995). The program uses the Cartesian coordinates of the centres of mass of each molecule, rotations around the molecule fixed axes and the six strain matrix elements as variables, so the relaxation of the crystal structure to a minimum in the lattice energy is not restricted to specific space groups. 

Lanthanide shift and relaxation probes have been used to show that the family of conformations of 5 -AMP in solution which most closely fits the NMR data is very similar to that of the crystal structure of AMP. This work (758) includes a description of the computer program used for the conformational searches. A subsequent study of cyclic 3, 5 -AMP (762) (Fig. 14) produced families of solution conformations with the pucker of the phosphate and ribose rings similar to that in an approximate X-ray study of the nucleotide. The solution conformation of 5 -CMP is found (763) to be similar to that of 5 -AMP. 

A variety of model catalysts have been employed we start with the simplest. Single-crystal surfaces of noble metals (platinum, rhodium, palladium, etc.) or oxides are structurally the best defined and the most homogeneous substrates, and the structural definition is beneficial both to experimentalists and theorists. Low-energy electron diffraction (LEED) facilitated the discovery of the relaxation and reconstruction of clean surfaces and the formation of ordered overlayers of adsorbed molecules (3,28-32). The combined application of LEED, Auger electron spectroscopy (AES), temperature-programmed desorption (TPD), field emission microscopy (FEM), X-ray and UV-photoelectron spectroscopy (XPS, UPS), IR reflection... 

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