Numerical study of the structural and vibrational properties of amorphous Ta_2O_5 and TiO_2-doped Ta_2O_5

摘要

Using classical molecular dynamics simulations, we synthesized amorphous Ta_2O_5 and amorphous TiO_2-doped Ta_2O_5. We show that Ta_2O_5 is composed primarily of six-folded Ta atoms forming octahedra that are either organized in chain-like structures or share edges or faces. When Ta_2O_5 is doped with TiO_2, Ti atoms form equally five- and six-folded polyhedra that perturb but do not break the network structure of the glass. Performing a vibrational eigenmode analysis and projecting the eigenmodes on the rocking, stretching, and bending motions of the Ta-2O and Ta-3O bonds, we provide an atomic-scale analysis that substantiates the interpretations of Raman spectra of amorphous Ta_2O_5. This eigenmode analysis also reveals the key role played by Ti atoms in the 5 to 12 THz range.