Epistemologia feminista: profunditzant sobre el coneixement situat (Part 1 de 4)

Ponent: Maria Puig de la Bellacasa / Presenta: Víctor Jorquera

Epistemologia feminista: profunditzant sobre el coneixement situat (part 2 de 4)

Ponent: Maria Puig de la Bellacasa / Presenta: Víctor Jorquera

Epistemologia feminista: profunditzant sobre el coneixement situat (part 3 de 4)

Ponent: Maria Puig de la Bellacasa / Presenta: Víctor Jorquera

Epistemologia feminista: profunditzant sobre el coneixement situat (part 4 de 4)

Ponent: Maria Puig de la Bellacasa / Presenta: Víctor Jorquera

Rigorous characterization of oxygen vacancies in ionic oxides

Charged and neutral oxygen vacancies in the bulk and on perfect and defective surfaces of MgO are characterized as quantum-mechanical subsystems chemically bonded to the host lattice and containing most of the charge left by the removed oxygens. Attractors of the electron density appear inside the vacancy, a necessary condition for the existence of a subsystem according to the atoms in molecules theory. The analysis of the electron localization function also shows attractors at the vacancy sites, which are associated to a localization basin shared with the valence domain of the nearest oxygens. This polyatomic superanion exhibits chemical trends guided by the formal charge and the coordination of the vacancy. The topological approach is shown to be essential to understand and predict the nature and chemical reactivity of these objects. There is not a vacancy but a coreless pseudoanion that behaves as an activated host oxygen.

Ab initio study of MF2 (M=Mn, Fe, Co, Ni) rutile-type compounds using the periodic unrestricted Hartree-Fock approach

The ab initio periodic unrestricted Hartree-Fock method has been applied in the investigation of the ground-state structural, electronic, and magnetic properties of the rutile-type compounds MF2 (M=Mn, Fe, Co, and Ni). All electron Gaussian basis sets have been used. The systems turn out to be large band-gap antiferromagnetic insulators; the optimized geometrical parameters are in good agreement with experiment. The calculated most stable electronic state shows an antiferromagnetic order in agreement with that resulting from neutron scattering experiments. The magnetic coupling constants between nearest-neighbor magnetic ions along the [001], [111], and [100] (or [010]) directions have been calculated using several supercells. The resulting ab initio magnetic coupling constants are reasonably satisfactory when compared with available experimental data. The importance of the Jahn-Teller effect in FeF2 and CoF2 is also discussed.