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

ABSTRACTFirst principles, total energy methods have been applied to predict the relative stabilities of the four experimentally verified MoC phases: the cubic δ(NaCl) phase and the three hexagonal γ(WC), η and γ′(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 γ phase was found to be the most stable followed by γ′, δ, and η, but for substoichiometric MoC0.75,MoC0.75, the order of relative stability was changed and the substoichiometric δ phase was found to have the lowest energy followed by γ′ and γ. 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–Mo bonds through the carbon vacancy site. Finally, the oxygen stabilization of the γ′ MoC phase was studied.

Eriksson, OlleUppsala universitet (author)
Nordström, LarsUppsala universitet (author)
Jansson, Ulf (author)
Fast, LarsÅngström Laboratory, Uppsala universitet (author)
Delin, AnnaÅngström Laboratory, Uppsala universitet (author)
Wills, John M.Los Alamos National Laboratory, Los Alamos, New Mexico (author)
Johansson, Börje (author)
Uppsala universitetÅngström Laboratory, Uppsala universitet (creator_code:org_t)

In:Journal of Applied Physics: AIP Publishing86:7, s. 3758-37670021-89791089-7550

By the author/editor: Hugosson, Håkan ...; Eriksson, Olle; Nordström, Lars; Jansson, Ulf; Fast, Lars; Delin, Anna; show more...; Wills, John M.; Johansson, Börje; show less...

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