Transition metals, segregation energies

Here, we will first briefly recall the principles of this method in the case of transition metals. Then we will apply it to two illustrative examples the surface segregation energy of an impurity is a pure host and the growth of adislands on FCC(lll) surfaces of the same chemical species. 

We will limit ourselves to the surface segregation energy of an impurity of atomic number Z + 1 in a BCC matrix of atomic number Z and study the variation of this energy as a function of the number Nj of d electrons per atom in the d band of e transition metal Z. 

Figure 2. Segregation energy in layer Sp (p = 0 surface layer...) of a transition metal impurity of atomic number Z + 1 (d band-filling (Nj + l.l)e /atom, full curves (Nj + l)e /atom, dashed curve) in a BCC transition metal matrix of atomic number Z (d band-filling Nje" /atom) for various crystallographic orientations of the surface...

M. Said, M. C. Desjonqudres and D. Spanjaard, Surface Core Level Shifts in BCC Transition Metals Deduced from Segregation Energy Calculation, Phys. Rev. B 47 4722 (1993)... 

Ruban AV, Skriver HE, Nprskov JK. 1999. Surface segregation energies in transition-metal alloys. Phys Rev B 59 15990-16000. 

GENERAL TRENDS FOR SURFACE SEGREGATION ENERGIES IN TRANSITION METAL ALLOYS... 

Fig. 6. Surface segregation energies of transition metal impurities (solute) for the closed-packed surfaces of transition metal hosts.

General trends for the surface segregation energies in transition metal alloys... 

A big amount of experimental studies of stability of many component systems Pt Me (where Me - transition metals Cr, Fe, Co, Ni, Ru) indicates about the formation of nanoclusters with core-shell structures [11-13], where mechanisms of the processes (including corrosive) with the formation of such structures are described. Firstly this is a surface segregation during the process of multicomponent nanocluster preparation [14], Due to such segregation nanocluster surface becomes enriched by one of the components, especially by platinum with the reduction of surface energy in segregated binary nanocluster [75]. In the process of corrosive influence (in model conditions or in tests of fuel cells) a prevailing dissolution of one component from basic metal Me and surface enrichment by platinum with the formation of a core-shell system. 

Nilekar AU, Ruban AV, Mavrikakis M (2009) Surface segregation energy in low-index open surfaces of bimetallic transition metal alloys. Surf Sci 603 91-96... 

Zhang Y, Duan Z, Xiao C, Wang G (2011) Density functional theory calculation of platinum surface segregation energy in PtsNi (111) surface doped with a third transition metal. Surf Sei 605 1577-1582... 

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