A Systematic Investigation on CrCu_n Clusters with n = 9–16: Noble Gas and Tunable Magnetic Property

Abstract

A systematic investigation on structure, dissociation behavior, chemical bonding, and magnetic property of Cr-doped Cun clusters (n = 9-16) is carried out using the mean of density functional theory calculations. It is found that CrCu12 is a crucial size, preferring an icosahedral Cu12 cage with the central Cr dopant. Smaller cluster sizes appear as on the way to form the CrCu12 icosahedron while larger ones are produced by attaching additional Cu atoms to the CrCu12 core. The presence of Cr dopant obviously enhances the stability of CrCun clusters in comparison to that of pure counterparts. Exceptionally stable CrCu12 has an 18-electron closed-shell electronic structure, mimicking a noble gas in the viewpoint of superatom concept. Analysis on cluster electronic structure shows that the interplay between 3d orbitals of Cr and 4s orbitals of Cu has a vital role on the magnetic properties of CrCun clusters.

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

“…We have recalculated the optimized geometries of Cu n Cr clusters (n = 9-11) using the BP86 functional with the basis sets cc-pvTZ-pp for Cu atom and cc-pvTZ for Cr atom to confirm the results presented in Ref. [23]. The previous investigation on ScCu n clusters also indicated that results obtained by the BP86 functional are well-matched to experimental values [21].…”

“…As one should be agreed that the Cu n Cr clusters (n = 9-11) possess a certain spin states. In the previous work [23], the results went to the same conclusion that the studied clusters exhibit a magnetic moment but the question about their magnetic origin has not been understood completely yet. By knowing where the unpaired electrons locate, in this report we could prejudge by our physical intuition that the unpaired electrons are on the 3d orbitals of Cr atom.…”

“…In the previous work, the spin states of Cu n Cr (n = 9-11) clusters have been well explained by the phenomenological shell [23] in which six outermost valence electrons of Cr atom (3d 5 4s 1 ) and n 4s 1 valence electrons of Cu atoms are assumed to freely delocalize and jointly form a molecular shell of the cluster. Taking that picture in mind, the quartet state of Cu 9 Cr can be understood in accordance to the particular electronic shell of 1S 2 1P 6 1D 7 with three unpaired electrons.…”

“…Recently, the investigation on Cu n Cr clusters (n = 9-16) has found that Cu 12 Cr is exceptionally stable and chemically inert as a superatomic molecule [23]. The magnetic moment of Cu n Cr clusters is governed mainly by the interaction between d-s valence orbitals of Cr and Cu atoms [23].…”

“…Recently, the investigation on Cu n Cr clusters (n = 9-16) has found that Cu 12 Cr is exceptionally stable and chemically inert as a superatomic molecule [23]. The magnetic moment of Cu n Cr clusters is governed mainly by the interaction between d-s valence orbitals of Cr and Cu atoms [23]. The magnetic moment of Cu n Cr (n = 9-11) clusters can be understood by incompleting electronic shell configuration 1S 2 1P 6 1D 9 for Cu 11 Cr, 1S 2 1P 6 1D 8 for Cu 10 Cr, and 1S 2 1P 6 1D 7 for Cu 9 Cr.…”