Growth patterns and structural motifs of cadmium clusters with up to 60 atoms: disordered or not?

Abstract

Using two different approaches, the structures of Cd clusters are optimized. At first, parameterized density-functional calculations using the DFTB method in combination with evolutionary algorithms provide one set of candidate structures. Second, earlier proposed structures based on the Gupta potential provide a second set. Subsequently, all structures of each set are re-optimized using parameter-free density-functional calculations. It turned out that those based on the DFTB calculations in almost all cases were those of the lowest total energy. By analysing the structural properties as a function of cluster size information on growth patterns can be extracted. Thereby, the results show a certain preference that the atoms of the inner parts have surroundings as found in bulk hcp Cd. Furthermore, for larger size ranges, we could identify a specific growth pattern, implying that most of these clusters cannot be classified as being disordered. The results show also that the 4d electrons have only a weak influence on the properties of the clusters that, however, is so strong that a jellium-like model occasionally becomes inaccurate in describing the properties. In particular, the question at which size the clusters can be considered to be metallic becomes non-trivial to answer. Further arguments based on a comparison of the HOMO-LUMO gaps with the Kubo gap, however, suggested the non-metallic properties in the studied size range.

Thickness-dependent characteristics and oxidation of 2D-cadmium

“…1, a bulk Cd structure constructed by metallic bonding of atoms to each other forms a hexagonal-close package structure that belongs to the space group of P 6 3 / mmc and the point group of D 6h . 19 Using total energy calculations, lattice parameters for the bulk structure are found to be a = b = 2.98 Å and c = 5.75 Å. However, as shown in Fig.…”

“…17 While Alvarez et al showed that metallicity of Cd n clusters emerges as a result of sp-hybridization, 18 and a study by Kohaut et al revealed that such clusters do not show metallic properties up to n = 60. 19 Besides, Oyeniyi et al developed and used a method to calculate the electronic excitation energies and absorption spectra of zero dimensional Zn, Cd and S clusters. 20 Xie et al demonstrated that nanoribbons of CdTe with their large photoresponse and high gain to visible NIR irradiation are promising candidates for photodetection applications.…”

Computational characterisation of structure and metallicity in small neutral and singly-charged cadmium clusters

“…As Cd is a group XII metal with a closed-shell electronic configuration, cadmium clusters are also considered to be ideal model systems to study the nature of the insulatorto-metal transition that must occur along the path bridging the dimer with the bulk limit 2 . However, the problem of characterizing the structure of cadmium clusters has been addressed only in a very limited number of computational works [3][4][5][6][7][8][9][10] , which moreover do not generally agree in the proposed global minimum (GM) structures. Experimental results about relative stabilities of charged cadmium clusters are also available [11][12][13] , which have not yet been convincingly reproduced and interpreted.…”