Diffraction studies on lattice vibration of fine particles of size less than a few hund-red angstroms in diameter are recently developed. The experimental method on the basis of the diffraction theory and the results in X-ray diffraction are described in detail. From the X-ray diffraction experiment on the temperature dependence of the integrated intensity in the Debye-Scherrer rings, the X-ray Debye temperature ΘM 156 K has been obtained for the fine particles of silver, whose size was about 150 Å in diameter. The Debye temperature of the fine silver particles is much lower than that of the bulk silver crystal, i. e. ΘM=212 K. This fact leads to the conclusion that the softening of lattice vibration is observed in the fine silver particles.
