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   COLLOQUIUM OF THE LABORATORY FOR COMPUTER DESIGN OF MATERIALS        
                   School of Computational Sciences	
                           (CSI 898-Sec 001) 
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     Initial oxidation of NiAl: What can we learn from ab initio
                                 calculations?

                             Alexander Y. Lozovoi

           Chemistry Department, University of Cambridge, U. K.

Adsorption at the surface of a multicomponent crystal with by a strong
interaction of the adsorbate with one of the components is a challenging
and practically important problem. An immediate example is given by the
selective oxidation of ordered intermetallic compounds, such as NiAl. Ab
initio density functional calculations provide us with the (free) energy
of the crystal surfaces with or without adsorbed oxygen atoms, and allow
us to optimize atomic positions in order to minimize the energy. However,
one should expect that the surface energies, and therefore the oxidation
process, would sensitively depend on the macroscopic parameters such as
oxygen partial pressure, temperature, and the substrate composition.  We
demonstrate that given the ab initio data at a given surface stoichiometry
[1], we are already in a position to study the oxidation process and its
dependence on the macroscopic parameters with just a little more
computational efforts. An approach to study the oxide/metal interface at a
variable oxygen partial pressure has previously been developed [2]. We now
extend that approach to the case of the surface of an intermetallic
compound. The additional ingredients necessary for treating this case,
namely the chemical potentials of the compound constituents, are obtained
as described in the previous work by Hagen and Finnis [3].

[1] A.Y. Lozovoi, A. Alavi, and M.W. Finnis, Phys. Rev. Lett. 85, 610
(2000).
[2] I.G. Batyrev, A. Alavi, and M. W. Finnis, Phys. Rev. B 62, 4698
(2000).
[3] M. Hagen and M.W. Finnis, Phil. Mag. A 77, 447 (1998).

                        Monday , April 23, 2001
                                  4:30 pm
                        Room 206, Science & Tech. I

Refreshments will be served at 4:15 PM.
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Find the schedule at http://csi.gmu.edu/lcdm/seminar/schedule.html