New Order-Parameter-Based Method for Characterizing Radiation Damage in Amorphous Materials

We present a new method of characterizing damage arising from α-recoil cascades in amorphous materials including glasses. The approach taken is topological, yielding information on atom connectivity and utilizing complete sets of orthogonal functions (spherical harmonics and Hermite functions) to compute order parameters. The utility of our new approach is demonstrated by first applying it to models of radiation-damaged crystalline zircon, enabling validation against the standard defect counting method (Wigner-Seitz). We then apply it to a simple model of a glass, obtained by supercooling a Lennard-Jones liquid, for which defect counting methods are inapplicable. The method shows great promise for use in characterizing damage in more complicated glasses, particularly those of interest in the immobilization of nuclear waste, and when used in conjunction with nonequilibrium computer simulation could be a powerful tool to elucidate experimental data on the radiation tolerance of such wasteforms.