Phase stability, structural and mechanical properties of transition metal nitrides using first principles calculations

Authors
Balasubramanian, Karthik
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Other Contributors
Gall, Daniel
Picu, Catalin R.
Huang, Liping
Lian, Jie
Koratkar, Nikhil A. A.
Issue Date
2018-05
Keywords
Mechanical engineering
Degree
PhD
Terms of Use
This electronic version is a licensed copy owned by Rensselaer Polytechnic Institute, Troy, NY. Copyright of original work retained by author.
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Abstract
Phase stability of Mo 1-x N x system: First-principles density-functional calculations coupled with the USPEX evolutionary phase-search algorithm are employed to calculate the convex hull of the Mo-N binary system. Eight Mo 1-x N x compound phases are found to be thermodynamically stable: tetragonal β-Mo 3 N, hexagonal δ-Mo 3 N 2 , cubic γ- Mo 11 N 8 , orthorhombic ε-Mo 4 N 3 , cubic γ-Mo 14 N 11 , monoclinic σ-MoN and σ-Mo 2 N 3 and hexagonal δ-MoN 2 . The convex hull is a straight line for 0 ≤ x ≤ 0.44 such that bcc Mo and the five listed compound phases with x ≤ 0.44 are predicted to co-exist in thermodynamic equilibrium. Comparing the convex hulls of cubic and hexagonal Mo x N 1-x indicates that cubic structures are preferred for molybdenum rich (x < 0.3) compounds, hexagonal phases are favored for nitrogen rich (x > 0.5) compositions, while similar formation enthalpies for cubic and hexagonal phases at intermediate x = 0.3 – 0.5 imply that kinetic factors play a crucial role in the phase formation.
Description
May 2018
School of Engineering
Department
Dept. of Mechanical, Aerospace, and Nuclear Engineering
Publisher
Rensselaer Polytechnic Institute, Troy, NY
Relationships
Rensselaer Theses and Dissertations Online Collection
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