A density-functional and molecular-dynamics study on the physical properties of yttrium-doped tantalum oxynitride

Fluorite-type phases in the system Y–Ta–O–N have been studied using both first-principle electronic-structure calculations and molecular-dynamic simulations to validate the structural data and to explain unusual asymmetric reflection profiles observed in the experimental X-ray diffraction patterns. We provide evidence that the compounds may be macroscopically described as to represent cubic fluorite-type defect structures despite the fact that DFT calculations clearly show that all crystallographic unit cells appear as triclinically distorted. Additionally, we find that there is a minute (but hardly significant) tendency for anionic ordering at absolute zero temperature but none under reaction conditions.

Structural result of a room-temperature molecular-dynamic simulation of a supercell of Y0.125Ta0.875O0.875N□0.125.Figure optionsDownload as PowerPoint slide