After the early 1970's, structural studies on the ferroelectric phase transition have been developed on the basis of the crystal structure analysis. The atomic order parameter, which characterizes atomic occupancies on local equilibrium positions, describes the order-disorder type phase transition. In case of the displacive type phase transition, fluctuations of the atomic positions, calculated from the temperature factor, become prominent with approaching the phase transition point. Several examples are presented for recently refined ferroelectric structures. [J. Cryst. Soc. Jpn, 28, 247 (1986) ] .
The crystallographic study of macrocyclic cyclophane inclusion compounds is reviewed. Cyclophanes such as [2.2.2], [6.6.6], [126.96.36.199] and [188.8.131.52] paracyclophanes and calixarenes with intramolecular hydrophobic cavities surrounded by benzene walls incorporate neutral guest molecules to give molecular inclusion compounds (cavitate) in solutions and in the solid state. Tri-o-thymotide forms chiral single crystals of cage type or channel type clathrate which have enantiomeric excess of guest molecules. [J. Cryst. Soc. Jpn. 28, 261 (1986) ] .
Recent development of ion scattering technique for study of the atomic arrangement of crystal surface is reviewed. Basic problems in the technique, both for keV ions and for MeV ions, are explained and some of the new ideas are mentioned for the further development of the technique. [J. Cryst. Soc. Jpn. 28, 273 (1986) ] .