Insights into the magnetic origin of CunCr (n = 9 ÷ 11) clusters: A superposition of magnetic and electronic shells

Abstract

Interests in Cu-Cr sub-nanometer systems have been increasing due to the recentlyfound icosahedral Cu12Cr cluster as a superatomic molecule, where the 3d-Cr and 4s-Cu electrons can phenomenologically form the 18-e molecular shell (1S21P61D10) of Cu12Cr. In this report, we set out to investigate the energetically-preferred geometries and stabilities of CunCr (n = 9÷11) clusters using the density-functional-theory calculations. It is found that not all of 3d-Cr electrons involve in the formation of the cluster shell and the remaining localized ones cause the magnetic moment of the clusters, which is different from what was believed. The calculated molecular diagram, natural orbital analysis, and spin-density computation are performed to elaborate our idea.