Ab initio simulation of $\mathrm{T}{\mathrm{a}}_2{\mathrm{O}}_5$: A high symmetry ground state phase with application to interface calculation

Abstract

We suggest a tetragonal $I{4}_1/amd$ phase ($\eta$-phase) as the ground state of $\mathrm{T}{\mathrm{a}}_2{\mathrm{O}}_5$ at zero temperature, which is a high symmetry version of the triclinic $\gamma$-phase $\mathrm{T}{\mathrm{a}}_2{\mathrm{O}}_5$ predicted by Yang and Kawazoe. Our calculation shows that $\gamma$-phase $\mathrm{T}{\mathrm{a}}_2{\mathrm{O}}_5$ will automatically be transformed into the $\eta$-phase during structural relaxation. Phonon dispersion confirms that the $\eta$-phase is dynamically stable, while the high temperature $\alpha$-phase $\mathrm{T}{\mathrm{a}}_2{\mathrm{O}}_5$, which also has the $I{4}_1/amd$ symmetry, is unstable at zero temperature. A thorough energy comparison of the ${\beta }_{AL}$, $\delta$, $\lambda$, $\mathrm{B}$, ${\mathrm{L}}_{\mathrm{SR}}$, ${\beta }_R$, $Pm$, $Cmmm$, $\gamma$, $\eta$ and $\alpha$ phases of $\mathrm{T}{\mathrm{a}}_2{\mathrm{O}}_5$ is carried out. The GGA-1/2 method is applied in calculating the electronic structure of various phases, where the $\eta$-phase demonstrates a 4.24 eV indirect band gap, close to experimental value. The high symmetry tetragonal phase together with computationally efficient GGA-1/2 method greatly facilitate the $abinitio$ simulation of $\mathrm{T}{\mathrm{a}}_2{\mathrm{O}}_5$-based devices. As an example, we have explicitly shown the Ohmic contact nature between metal Ta and $\mathrm{T}{\mathrm{a}}_2{\mathrm{O}}_5$ by calculating an interface model of $b.c.c.$ Ta and $\eta$-$\mathrm{T}{\mathrm{a}}_2{\mathrm{O}}_5$, using GGA-1/2.

27 pages, 8 figures

References in corpus (5)

• Restoring the density-gradient expansion for exchange in solids and surfaces
• Generalized gradient approximation for solids and their surfaces
• An approximation to density functional theory for an accurate calculation of band-gaps of semiconductors
• Improved self-energy correction method for accurate and efficient band structure calculation
• Prediction of New Ground State Crystal Structure of Ta2O5

Cited by in corpus (4)

• Global optimization of atomic structures with gradient-enhanced Gaussian process regression
• Structural and Electronic Properties of Ta2O5 with One Formula Unit
• On the self-consistency of DFT-1/2
• Ab initio Phase Diagram of Ta2O5