Theory of phase stabilities and bonding mechanisms in stoichiometric and substoichiometric molybdenum carbide

Journal Article · Fri Oct 01 00:00:00 EDT 1999 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.371284· OSTI ID:686437

Hugosson, H W; Eriksson, O; Nordstroem, L ^[1]; Jansson, U ^[2]; Fast, L; Delin, A ^[1]; Wills, J M ^[3]; Johansson, B ^[4]

---

1. Condensed Matter Theory Group, Department of Physics, University of Uppsala, Box 530, S-751 21 Uppsala (Sweden)
2. Inorganic Chemistry Group, Angstroem Laboratory, Box 538, S-751 21 Uppsala (Sweden)
3. Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87544 (United States)
4. Condensed Matter Theory Group, Department of Physics University of Uppsala, Box 530, S-751 21 Uppsala (Sweden)

First principles, total energy methods have been applied to predict the relative stabilities of the four experimentally verified MoC phases: the cubic {delta}(NaCl) phase and the three hexagonal {gamma}(WC), {eta} and {gamma}{sup {prime}}(TiAs) phases. The effect of vacancies on the relative stability of these four phases was investigated using a model structure with ordered vacancies within the carbon sublattice. For stoichiometric MoC, the {gamma} phase was found to be the most stable followed by {gamma}{sup {prime}}, {delta}, and {eta}, but for substoichiometric MoC{sub 0.75}, the order of relative stability was changed and the substoichiometric {delta} phase was found to have the lowest energy followed by {gamma}{sup {prime}} and {gamma}. A study of the electronic structure revealed vacancy induced peaks in the density of state and the electron density attached to these peaks was analyzed and found to emanate from unscreened Mo{endash}Mo bonds through the carbon vacancy site. Finally, the oxygen stabilization of the {gamma}{sup {prime}} MoC phase was studied. {copyright} {ital 1999 American Institute of Physics.}

• OSTI ID: 686437
• Journal Information: Journal of Applied Physics, Vol. 86, Issue 7; Other Information: PBD: Oct 1999
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
MOLYBDENUM COMPOUNDS
MOLYBDENUM CARBIDES
BONDING
STOICHIOMETRY
PHASE DIAGRAMS
STABILITY
VACANCIES
STRUCTURAL MODELS
ELECTRONIC STRUCTURE
ELECTRON DENSITY