Sub-lattice Melting in Amorphous Tantala

We use molecular dynamics to investigate amorphous tantala and doped tantala. We found an interesting sub-lattice melting phase during annealing process. Our simulation shows that in this particular phase only oxygen is diffusive while tantalum is not. The calculated self-diffusion coefficient of oxygen is about 100 times larger than that of tantalum, or is in the order of 10^-5 cm²/s at around 2000K. Simulations are also performed for Zr- and Ti-doped tantalum oxides, and the dopant effects are analyzed.