Abstract
We perform first-principles density functional calculations on a newly discovered tantalum nitride with an orthorhombic structure to assess its thermodynamic and mechanical stabilities. Our random search unveils a tetragonal structure that is energetically more favorable than an orthorhombic at zero pressure. We predict that the tetragonal transforms into the orthorhombic phase above a relatively low pressure of 7.7 GPa. Single-crystal elastic constant calculations reveal that orthorhombic is mechanically unstable because of a negative . Our calculations suggest that minor oxygen substitution for nitrogen plays an important role in stabilizing the orthorhombic structure.
- Received 1 August 2009
DOI:https://doi.org/10.1103/PhysRevLett.103.185501
©2009 American Physical Society