First Principles Study on Ta$_{25 }$ Low- and High-Temperature Phases

Low- and high-temperature phases of Tantalum pentoxide (Ta$_{2}$O$_{5})$ have been studied by density functional method. Our calculations have been carried out using the projector-augmented wave method and a plane wave basis set. Tantalum pen-oxide, Ta$_{2}$O$_{5}$ is considered as a potential alternative to SiO$_{2}$ because of its high breakdown voltage, its high dielectric constant, and its excellent step coverage characteristics. It is also a dielectric material for optical coating application that is important to high precision instrumentation. We have studied structure, electronic properties, and phonon spectra, as well as elastic modulii, including bulk modulus, Young's modulus and Poisson's ratio. Four different isomorphs will be presented. Furthermore, SiO$_{2}$-doped Ta$_{2}$O$_{5}$, which is used as mirror coatings in current interferometric gravitational wave detectors, has also been investigated. Our results help to understand the properties of this material in different phases.