Novel quantitative interpretations are presented for the heteroepitaxy of Au deposited onto UHV-cleaved surfaces of NaCl and KBr. Although Au adsorption processes in the (100) surface of alkali-halide crystals have been regarded as physisorption so far, the result of simulation by the discrete variational Xα cluster method confirms that a Au atom adsorbs to make chemically bonding states on both the NaCl (100) and KBr (100) surfaces. The present well-controlled UHV deposition experiments offer the following results : In the Au/ NaCl system, multiply twinned particles (MTP's) are formed; on the other hand, in the Au/ KBr system, pyramidal particles which are a single crystal are formed. This result suggests that the Au atom is more strongly bonded on the KBr surface than the NaCl one. However, the simulated results are opposite. Therefore, it is proposed that in the heteroepitaxy of a metal/alkali-halide system the strength of chemical bonding is not a decisive parameter, but the geometric factors such as surface dangling bond and symmetry of the atomic arrangements of a substrate play an important role.
Application of Secondary ion mass spectrometry (SIMS) to the study of chemical analyses of insulated materials is described. A simple working curve method is useful for the quantitative analyses of SIMS data. The sensivity acheaved is suffietient to concentration levels from ppm to ppb. This is demonstrated for the partition coefficients between olivine and magma and for the impuriry destribution in diamond thin film. A blieaf description of two demensional analyses is also made.
Multiwavfelength X-ray diffraction studies were performed on cytochrome c' (Cyt. c') and superoxide dismutase (SOD) crystals. Multiwavelength intensity data were collected for the crystals using synchrotron radiation produced by the vertical wiggler at the Photon Factory, National Laboratory for High Energy Physics. Positions of two irons in the Cyt. c' crystal were determined from difference Patterson maps based on anomalous scattering caused by irons. Fourier maps calculated from the multiwavelength data indicated clear molecular boundaries. Positions of the Cu2+ and Zn2+ sites in the crystal of SOD were located and distinguished from difference Fourier maps by enhancing anomalous scattering effects of Cu2+ and/or Zn2+.
The structures of icosahedral and decagonal quasicrystals are discussed from highresolution electron microscope observations of Al-Mn-Si icosahedral and Al-Mn decagonal quasicrystals. A high-resolution micrograph of the Al-Mn decagonal quasicrystal taken with the incidence parallel to the 10-fold symmetry axis shows a pattern of an aperiodic tiling with two types of rhombs, which is distinguished from the Penrose tiling with matching and inflation rules. An image of the Al-Mn-Si icosahedral quasicrystal is interpreted by the projection of the 3-dimensional Penrose tiling. In the Al-Mn-Si icosahedral quasicrystal, quench-ed phason strains and dislocations were obserbed.
The gold clusters, less than 50 A in diameter, became structurally unstable under the electron beam irradiation (105 electrons/A2. sec) and continually changed their shapes; single, twinned and multiply-twinned crystals. Two possibilities for causing the instability can be thought; specimen temperature rise or surface charging due to secondary electron emission. Electron microscope observation utilizing a fine-focused electron beam favors to the surface charging effect. Reorganization of atoms in the clusters, often undergoing in the twin deformation, was caused by a shear stress due to a coulomb force arising from the positive surface charges.