Reminiscences are given out of the early stages of the development in x-ray crystallography, both in Japan and abroad. Activities in Prof. Ewald's school in Germany, those of Prof. Bragg's in England, Prof. Terada's and Nishikawa's in Japan are described. Prof. Nishikawa's contribution concerning the space group theory in the structure analysis is brought to attention. Early works of Prof. Nitta on organic crystals are also described. Some x-ray photographs taken by Prof. Nishikawa and Prof. Nitta in the early period from 1913 to 1925 are reproduced. (abstract by the editor)
The rotation function has been widely used in the initial stages of the solution of protein structures. It was theoretically developed by M. G. Rossmann and D. M. Blow. The rotation function by R. A. Crowther can afford very much faster computation of the same function in Eulerian space. Its expression is recasted by the present author in another form which makes it convenient to explore in spherical polar coordinates rather than in Eulerian angles.
Scapolite is a series of tetragonal alumino-framework silicates with two formula units per cell, and is a solid solution between marialite, Na4 Al3 Si9 O24 Cl, and meionite, Ca4 Al6 Si6 O24 CO3. There are two substitution systems according to its composition: from marialite end-member to 75% meionite, Ca2 Al2·CO3 are substituted for Na2 Si2·NaCI, and from 75% meionite to meionite end-member, NaSi are replaced with CaAI as in plageoclase feldspars. The crystal structure of scapolite is characterized by the three dimensional framework of (Al, Si) -O tetrahedra and by both large cation and anion groups in the cavity of the framework. The space group of theoretical end-members is I4/m, but intermediate compositions have weak b-reflections, which violate body centered symmetry, and thus their space group is reduced to P42/n. Al and Si atoms distributed in the three distinct tetrahedral sites are in the most highly ordered fashion at 37.5% meionite. Position of Na and Ca atoms in the same site is also most shifted at 37.5% meionite in the solid solution. So at around this composition, the crystal structure is most distorted from those of end-members and, consequently, the intensities of the additional b-reflections become maximum. The a cell dimension and the unit cell volume linearly increase while c decreases with increased meionite component.