Ab Initio Simulation of Ta 2 O 5 : A High Symmetry Ground State Phase with Application to Interface Calculation

• Published in: Annalen der Physik Vol. 531; no. 8
• Main Authors: Yuan, Jun‐Hui, Xue, Kan‐Hao, Chen, Qi, Fonseca, Leonardo R. C., Miao, Xiang‐Shui
• Format: Journal Article
• Language: English
• Published: 01.08.2019
• ISSN: 0003-3804; 1521-3889
• DOI: 10.1002/andp.201800524

Abstract It is reported that the recently predicted triclinic γ‐phase ground state Ta 2 O 5 by Yang and Kawazoe can be assigned a much more symmetric I 4 1 / amd space group, and is isomorphic to P‐Nb 2 O 5 . Interestingly, the well‐known high temperature α‐phase Ta 2 O 5 also has the I 4 1 / amd symmetry, but is unstable at zero temperature according to our phonon dispersion calculation. A thorough energy comparison of the β AL , δ, λ, Β, L SR , β R , Pm , Cmmm , γ, and α phases of Ta 2 O 5 is carried out using density functional theory under the generalized gradient approximation (GGA). The GGA‐1/2 method is applied in calculating the electronic structure of various phases, where the tetragonal γ‐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 facilitates the ab initio simulation of Ta 2 O 5 ‐based devices. As an example, the Ohmic contact nature between metal Ta and Ta 2 O 5 by calculating an interface model of b.c.c . Ta and tetragonal γ‐Ta 2 O 5 , using GGA‐1/2 has been explicitly shown.