A computational search for the zeta phase in the tantalum carbides
Abstract
A systematic electronic structure density functional theory search for the zeta phase in the tantalum carbon system has been conducted, demonstrating that the zeta phase does indeed lie on the convex hull, establishing low‐temperature thermodynamic stability, and is structurally stable. Even though the zeta phase is most oft reported as a ζ‐Ta4C3‐x structure, these new computational results reveal that the perfectly ordered zeta phase occurs at the Ta3C2 composition and belongs to the C2/m space group. Furthermore, these results suggest that the space group may be a result of an order‐disorder transition and potential deviations from ideal stoichiometry at higher temperatures. The structure of this Ta3C2 compound can be described as ordered strings of carbon vacancies on a single carbon plane, which is also the preferred plane where additional carbon vacancies or interstitials form. These defects have modest formation energies, which provides further explanation for the small homogeneity range in zeta phase.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Aug 14, 2018
- Source ID
- 10.1111/jace.15970
Entities
People
- Christopher R Weinberger
- Gregory B. Thompson
Organizations
- Air Force Office of Scientific Research
- Colorado State University
- National Science Foundation
- University of Alabama