In the last decade the pressure-induced amorphization of several crystals such as SiO2, Ca (OH) 2, H2O, GeO2, α-AlPO4 etc. have been found under compression at room temperature. The pressure-induced amorphization was previously regarded as the thermodynamically metastable phase, which corresponds the super cooled liquid phase at room temperature. The amorphization is a precursor phenomenon of the phase transition to the high pressure form. There are two different types of the reversible and irreversible amorphization. Dynamical lattice-instability due to shear and stress induces the reversible amorphization, which produces memory glass. On the other hand the irreversible mode is attributed to the nucleation of highpressure form in the parent lattice but thermal energy is not high enough to provide the large crystallite size coherent to the X-ray wave length. The successive structure change of the pressure-induced amorphizaiton was investigated under various pressure and temperature by X-ray diffraction study, XAFS and Raman spectroscopy with diamond anvil pressure cell.
Electrical conductance of point contacts between a metal tip and semiconductor surfaces has been measured with scanning tunneling microscope (STM) . The conductance depends strongly on the electronic structures of semiconductor surfaces. It also changes with a distribution of steps around its contact area. These results suggest that it is due to the conductivity via surface electronic states, that is, surface state conductivity.
The extended electrostatic valence rule is applied to several superconductors and related compounds to explain differences in interatomic distances within coordination polyhedra. A general structural feature is indicated that bonds between apical oxygen and atoms opposite to Cu on CuO2 sheets are relatively short and covalent. A new method in conformity with this idea is proposed for describing the crystal structures of superconductors.
X-ray prortein crystallography is now applied to the analysis of large protein complex system, however, there still exists a problem in its application, that is X-radiation damage of protein crystals. To reduce radiation damage, cryogenic experiment at liquid nitrogen temperature is the best way. In order to utilize the method, some experimental procedures have to be developed; addition of anti-freezing reagent, crystal mounting device, rapid cooling method. Here, the author descrives the important aspects of each procedure and some results of cryogenic experiments.