Introduction to elementary protein crystallography including items such as, features of protein crystals, crystallization of proteins, the heavy atom isomorphous replacement method, model building and refinement, and a brief history of proten crystallography, is presented.
It is known that ordered structures appear in III-V semiconductor alloys grown by vapor phase epitaxy. The existence of these ordered phases is unexpected from the equilibrium phase diagram for the bulk III-V alloys. In order to clarify the formation mechanism of the ordered structures in epitaxially grown III-V semiconductor alloys, we have proposed a simple kinetic Ising model for the epitaxial growth and carried out Monte Carlo simulations of the microstructural evolution based on the proposed model. This article is concerned with the CuAu-I (L10) and CuPt (L11) type ordering in the epilayers grown on exact (001) substrates. The simulated microstructures and their Fourier power spectra are in excellent agreement with those revealed by electron microscopy and diffraction. This suggests that our crystal growth model is quite useful in discussing the ordering kinetics and phase state in epitaxially grown layers. We also refer to the interfacial spinodal decomposition, which often occurs in liquid phase epitaxy.
In situ X-ray diffraction measurements of the phase transformations in serpentine have been carried out using a multianvil high-pressure system combined with synchrotron radiation. Serpentine persisted upon compression to 28 GPa at a room temperature, while it became amorphous in a limited temperature interval of 200-400°C at pressures above 13 GPa. A rapid crystallization of high pressure phases then started at temperatures greater than about 400°C. These observations suggest that the amorphization of serpentine is an unlikely mechanism of deep-focus earthquakes associated with subduction of slabs, as the temperatures of these slabs are generally higher than those of the rapid crystallization regime.
The structure of the CaF2/Si (111) interface has been investigated with the use of X-ray crystal truncation rod scattering. The T -site which is just above the first layer Si atom is occupied by an interfacial Ca atom for a type-A interface as well as for a type-B interface. Structural parameters, describing the interface and the structure of the thin film have also been obtained and discussed thoroughly. Crystallinity of the type-A epilayer and that of the type-B epilayer has been compared. For type-B thin film, there is an evidence that a shortinterface-spacing-structure is not an equilibrium state, but can transform to a long-interfacespacing-structure. We are able to gain insight into a possibility that the type-A structure can also transform to a different structure.
Metastable crystal structures of very thin Co and Fe layers in Au/Co (001) and Au/Fe (001) superlattice films characterized by X-ray diffraction are described. Cobalt films thinner than 1.0 nm grow pseudomorphologically with bct structures. Iron films thinner than 1.5 nm show an anomalous tetragonal distortion. Investigations of metastable structures in some other metallic superlattices have been also reviewed.
X-ray crystallographic studies were carried out for conglomerate salts, racemic-compound salts, and enantiomerically pure salts of chiral primary amines with achiral mono-carboxylic acids. The crystal structures of the conglomerate salts revealed that these crystals can be regarded as being a supramolecular assembly of a characteristic columnar hydrogen-bond network, in which the ammonium cations and the carboxylate anions are aligned around a twofold screw axis (21-column) . On the other hand, the crystal structures of the racemic-compound salts could be roughly classified into two types. One type is a crystal consisting of 21columns; the other type is a crystal consisting of a different type of columnar hydrogen-bond network, in which the ammonium cations and the carboxylate anions are related by inversion centers (i-column) .These results suggest that both the formation and the assembly of 21columns are essential in the formation of conglomerates for these salts.