First principles study of electronic structure for cubane-like and ring-shaped structures of M4O4, M4S4 clusters (M = Mn, Fe, Co, Ni, Cu)

Soumendu Datta,Badiur Rahaman

doi:10.1063/1.4936561

Soumendu Datta, Badiur Rahaman

Open Access

https://doi.org/10.1063/1.4936561

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Abstract

Spin-polarized DFT has been used to perform a comparative study of the geometric structures and electronic properties for isolated M4X4 nano clusters between their two stable isomers - a planar rhombus-like 2D structure and a cubane-like 3D structure with M = Mn, Fe, Co, Ni, Cu ; X = O, S. These two structural patterns of the M4X4 clusters are commonly found as building blocks in several poly-nuclear transition metal complexes in inorganic chemistry. The effects of the van der Waals corrections to the physical properties have been considered in the electronic structure calculations employing the empirical Grimme’s correction (DFT+D2). We report here an interesting trend in their relative structural stability - the isolated M4O4 clusters prefer to stabilize more in the planar structure, while the cubane-like 3D structure is more favorable for most of the isolated M4S4 clusters than their planar 2D counterparts. Our study reveals that this contrasting trend in the relative structural stability is expected to be driven by an interesting interplay between the s-d and p-d hybridization effects of the constituents’ valence electrons.

Highlights

INTRODUCTIONDiffering from their bulk behavior,[9] which renders them many unusual properties. several oxide nano clusters exhibit some magic sizes and compositions which correspond to unusually high stability.[10]
After the discovery of graphene and carbon fullerene based nano structures, the molecular clusters having cage-like as well as planar geometries have attracted much attention for constructing novel high-tech nano-materials
Spin-polarized density functional theory (DFT) has been used to perform a comparative study of the geometric structures and electronic properties for isolated M4X4 nano clusters between their two stable isomers - a planar rhombus-like 2D structure and a cubane-like 3D structure with M = Mn, Fe, Co, Ni, Cu ; X = O, S

Summary

INTRODUCTION

Differing from their bulk behavior,[9] which renders them many unusual properties. several oxide nano clusters exhibit some magic sizes and compositions which correspond to unusually high stability.[10]. It is interesting to follow-up that several molecular beam experiments on the isolated MmOn oxide clusters of the 3d late transition metal M atoms indicate a preference for the M:O ratio as 1:1 in case of the smaller cluster sizes.16–19Attempts of searching for the structures of the smallest building blocks in the structures of such oxide nano particles, have been offered recently by some first principles theoretical calculations.[20,21] We will concentrate here on the structure, electronic and magnetic properties of the isolated and isoatomic M4O4/M4S4 molecular building blocks with the metal atom M corresponding to one of the 3d late transition metal atoms i.e. Mn, Fe, Co, Ni or Cu. Note that ring-shaped planar structures as well as cage-shaped structures have been predicted widely as the two competing stable isomers for the small clusters of most of the TM oxides.[22,23] Our aim, in this work, will be, to perform a rigorous relative structural stability analysis of each.

COMPUTATIONAL DETAILS

RESULTS AND DISCUSSIONS

SUMMARY AND CONCLUSIONS