THEORY OF INSTABILITY PHENOMENA IN CRYSTALS

Crystal instability due to anharmonic lattice vibrations is discussed by applying the self-consistent Einstein theory to three-dimensional c rystals. It is shown that there exists a mode connected with the cryst al instability which depends on the crystal structure and symmetry. Us ing this theory, the structure of amorphous metals has been studied. I t is found that the structural unit in an amorphous state prepared fro m a face-centered cubic crystal forms an icosahedron with 13 atoms.