Microscopic theory of covalent-ionic transition of amorphizability of nonmetallic solids.

Under heavy ion bombardment more covalent A(n)B(8-n) crystals become amorphous while more ionic ones do not. The critical ionicity (Phillips Scale) which separates these two classes is f(i)(ac)=0.41, so that AlN(f(i)=0.45) is grouped with II- VI and I-VII as non-amorphizable. Several thermomechanical defect models are discussed and are found to give values of f(i)(ac) which are too high.