THE ROLE OF TOPOLOGY AND GEOMETRY IN THE IRRADIATION-INDUCED AMORPHIZATION OF NETWORK STRUCTURES

Network structures are characterized by some measure of directed bondi ng and more arbitrary connectivity. Crystalline networks additionally exhibit long-range translational periodicity and orientational order. The irradiation-induced loss of both latter features - commonly known as amorphization and geologically as metamictization - actually repres ents a loss of topological order and provides a measure of the structu ral redundancy in the network. Because of its similarity to glass form ation, the metamict transition can provide potential insights into the structures of network glasses. High-resolution electron microscopy an d energy-filtered electron diffraction provide important, though unfor tunately limited, information about the process and the products of th e topological disordering.