Origin of asymmetric growth during solid-state amorphization studied with molecular-dynamics simulation

Solid-state interfacial reaction in the Ni/Nb multilayers upon thermal annealing is investigated with molecular-dynamics simulation. The result shows that amorphization takes place at medium temperatures and the growth of the amorphous interlayer presents an asymmetric behavior due to faster consuming of the Ni layer than the Nb layer. Consequently, a Ni-enriched amorphous phase is formed together with some unreacted Nb before complete amorphization, which agrees well with the experimental observations. Moreover, it is revealed that the Nb lattice can accommodate a large number of Ni atoms and still retain crystalline structure, while a small amount of Nb atoms induce a spontaneous decay of the Ni lattice, which is essentially the physical origin of the asymmetric growth observed in not only the Ni-Nb system but also in the other systems studied so far. (C) 2000 American Institute of Physics. [S0021-8979(00)04311-5].