Cage-like Clusters With Transition Metals:Ab Initio Prediction Of Configurations And Properties

The study of clusters is important to understand the evolution of matters from atoms to solids,and determining the geometry of clusters is the key to studying its physicochemical properties.At present,it is not possible to directly measure the ground state of multiple atomic free clusters,therefore,it is necessary to theoretically establish structural models of clusters to predict and explain the experimental phenomena.In this paper,we constructed a series of stable clusters based on first-principles calculations.The electronic properties of these clusters have also been studied.(1)A stable hollow cage,which contains 42 gold atoms and 20 nitrogen atoms,has been investigated using first-principles studies.This Au₄₂N₂₀ cage has an I_h group symmetry and a shape like Catalan deltoidal hexecontahedron.Molecular dynamics simulations demonstrate that the Au₄₂N₂₀ cage retains its geometric topology up to about 1317 K.Vibration frequency analysis with no imaginary frequencies also indicates the stability of the Au₄₂N₂₀ molecule.The analysis for the bonding characteristic and electronic structure shows that the p–d hybridization near the Fermi level,which may be the key to the stability of the Au₄₂N₂₀ cage.The large negative nucleus-independent chemical shift value demonstrates its strong aromaticity.Furthermore,the Au₄₂N₂₀ molecule with high surface area may have potential applications in catalysis.(2)A chiral molecule with octahedral symmetry,Re₆C₃₂,as a hollow magnetic Catalan pentagonal icositetrahedron cage,has been identified using first-principles calculations.The calculated vibrational frequencies are in the range of 83.0-1341.2 cm^-1,which indicate the high mechanical stability of the Re₆C₃₂molecule.Moreover,the topological structure is well maintained up to 1500 K by ab initio molecular dynamics simulations,which indicates its thermodynamic stability.Analysis of the electronic structure shows that there is significant p-d orbital hybridization near the Fermi level,which is important to the structural stability of the Re₆C₃₂molecule.Furthermore,this Re₆C₃₂molecule is a magnetic cage with total spin magnetic moment of 12?_B.This magnetic carbon-based hollow cage may become a candidate for single-molecule devices.(3)Here we constructed a C₆₀Cu₃₀S₆₀ molecule with high I_h symmetry which can be viewed as consisting of 12 Cu₃(C₆S₆),which is the subunit of the copper coordination polymer[Cu₃(C₆S₆)]_n with superconducting phase.Born-Oppenheimer molecular dynamics simulations demonstrate that the topological structure of cage-like C₆₀Cu₃₀S₆₀ molecule was well maintained when the effective temperature is up to 710 K.The analysis for the PDOS and molecular orbitals shows clear characteristics of p-d hybridization near the Fermi level.The results of the electronic properties for C₆₀Cu₃₀S₆₀presented that the Cu-3d states make the main contribution to form Cu-S bonds,which may help us to understand why the Cu-containing structures can form sheets or cages.In addition,considering that Au atoms and Cu atoms belong to the same family of elements,and the Au atoms have similar extra-nuclear electron number distributions,a stable C₆₀Au₃₀S₆₀ cluster with I_h symmetry has also been proposed.Molecular dynamics simulations show that the C₆₀Au₃₀S₆₀ molecules have higher thermodynamic stability than the C₆₀Cu₃₀S₆₀ molecule,and the analysis for the electronic properties shows that the C₆₀Au₃₀S₆₀ molecule presents similar electronic properties as the C₆₀Cu₃₀S₆₀ molecule.(4)To further understand the bonding characteristics,we analyze the natural bond orbitals of the two-dimensional Sc C sheet with planar-tetracoordinate structure and the Au₃C₈ sheet with honeycomb structure.We find that the?bonds between the Sc atoms and C atoms in the tetragonal Sc C single-layer sheet,which are formed due to the contributions of the d electrons of the Sc atoms and the sp³ hybridization of C atoms,play important role in the stability of the Sc C sheet.For the two-dimensional Au₃C₈ sheet with a honeycomb structure,the?bonds between the Au atoms and C atoms,and the?bonds and?bonds between two adjacent C atoms are the keys to structural stability.