Construction of Interatomic Potentials and Mechanical Loss in Nb₂O₅

A BKS-Morse empirical potential is constructed for the B and H phases of Niobium Pentoxide (Nb₂O₅) for molecular dynamics simulation and energy landscape characterizations. Parameters of the interatomic potentials were adjusted to reproduce elastic properties of the two phases of Nb₂O₅ simultaneously. Given the absence of experimental data, we compared these elastic properties to those obtained using density function theory (DFT) calculations. We applied the potential to study amorphous Nb₂O₅ with structures generated by melting-quench classical molecular dynamics (MD) simulations. We then systematically located energy barriers for two-level systems. The energy barrier distribution collected from ~10⁴ barriers can be compared to experiments. We use the distribution function and calculated relaxation time, mechanical coupling constants, etc. to obtain the mechanical loss (Q^-1), which is of importance to optical coating materials for the future generation of gravitational wave detection.