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How to determine accurate chemical ordering in several nanometer large bimetallic crystallites from electronic structure calculations


How to determine accurate chemical ordering in several nanometer large bimetallic crystallites from electronic structure calculations

S.M. Kozlov, G. Kovács, R. Ferrando, K.M. Neyman

Chem. Sci., 6 (2015) 3868.

4.4 nm nanoparticles composed of > 1400 atoms

Nanoalloys have a new degree of freedom compared to monometallic particles – the chemical ordering (COR) – the pattern, in which different atoms are located in the particle. The COR defines surface reactivity of nanoalloys. Experimental determination of the COR in bimetallic particles is very laborious. Also, calculation of the COR is a great challenge due to enormous number of possible mutual atomic positions in nanoparticles. We proposed an innovative method to accurately ascertain the COR using results of only several density functional calculations. This method immediately reveals why a certain COR is preferred. We unravelled the COR and binding nature in Pd70Au70, Pd70Ag70, Pd70Cu70 and Pd70Zn70 nanoparticles. The power of the method is also illustrated by optimizing the COR in larger Pd732Au731, Pd732Ag731, Pd732Cu731 and Pd732Zn731 particles, whose size ~4.4 nm is common in catalytic applications.