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

Network structures are characterized by some measure of directed bonding 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 represents a loss of topological order and provides a measure of the structural redundancy in the network. Because of its similarity to glass formation, the metamict transition can provide potential insights into the structures of network glasses. High-resolution electron microscopy and energy-filtered electron diffraction provide important, though unfortunately limited, information about the process and the products of the topological disordering.