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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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            Surface segregation in transition metal alloys

                             A.V. Ruban

  Center for Atomic-Scale Materials Physics, Department of Physics,
          Technical University of Denmark, Lyngby, Denmark.

The surface segregation phenomenon is discussed in 1) dilute alloys, 2)
random concentrated alloys and 3) ordered phases. In the first case the
general trends in the surface segregation energies are established and
explained. Calculated surface concentration profiles for some alloys are
compared with experimental data. The surface orientation and alloy
composition dependence is demonstrated and discussed. It is shown that the
surface composition of an ordered phase is strongly influenced by its
stoichiometric composition (off-stoichiometric effect). The results are
obtained either by total energy calculations by the KKR-ASA(+M)
(Korringa-Kohn-Rostoker method in the atomic sphere approximation with
multipole moment correction) combined with the CPA (coherent potential
approximation) in the case of random and partially ordered alloys, or from
the effective cluster interactions obtained by the generalized
perturbation method (GPM) which includes electrostatic correction.
Calculations of the concentration profiles have been carried out either in
the single-site mean field approximation or by a Monte Carlo method in the
grand canonical ensemble.

                        Monday , February 19, 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