Investigation of the chemical ordering and thermal properties of the Rh–Ag–Au nanoalloys

In this paper, the melting behaviors of Rh–Ag–Au nanoalloys are investigated with MD simulation. For Rh–Ag–Au nanoalloys, icosahedron structure was considered. The local optimizations of Rh–Ag–Au nanoalloys were carried out with the BH algorithm. The interatomic interactions were modeled with the Gupta potential. The local optimization results of Rh–Ag–Au nanoalloys show that Au and Ag atoms prefer to locate on the surface, and Rh atoms prefer to locate in the inner shells. The bond order parameter result is compatible with the excess energy analysis. It is noted that structures with more Ag–Au bonds are more energetically stable. Caloric curve, heat capacity, Lindemann index, and RMSD methods were used for estimating the melting temperatures of Rh–Ag–Au nanoalloys. According to the simulation results, melting temperatures depend on the composition. Also, it is discovered that nanoalloys are generally melting in two stages. Surface melting of the third shell is occupied by Ag and Au atoms, and then homogeneous melting of the inner shells is occupied by Rh atoms. It is found that the difference between surface melting temperatures and homogeneous melting temperatures in Ag-poor compositions is more significant than that of Ag-rich nanoalloys. In addition, the melting temperatures of the nanoalloys are found to be increased as the size of nanoalloys increases.

Structural and dynamics properties of double icosahedral Pd-Ag-Pt trimetallic clusters

Using Monte Carlo Basin-hopping algorithm within the Gupta potential, a systematic investigation has been performed for the best chemical ordering structures of 19-atom trimetallic [Formula: see text] nanoclusters with double icosahedral geometry. The structures with the lowest energy at Gupta level are then re-optimized by DFT relaxations and the DFT relaxations confirmed the lowest energy structures obtained at the Gupta level indicating the double icosahedron structure is favorable for 19-atom [Formula: see text] nanoclusters. It was observed that the caloric curves exhibit a smoother transition with structural isomerizations other than a sharp jump behavior.

Theoretical study of the structures of bimetallic Ag–Au and Cu–Au clusters up to 108 atoms

The stable structures of Ag–Au and Cu–Au clusters with 1 : 1, 1 : 3 and 3 : 1 compositions with up to 108 atoms are obtained using a modified adaptive immune optimization algorithm with Gupta potential. The dominant motifs of Ag–Au and Cu–Au clusters are decahedron and icosahedron, respectively. However, in Ag-rich Ag–Au clusters, more icosahedra are found, and in Cu-rich Cu–Au clusters, there exist several decahedral motifs. Four Leary tetrahedral motifs are predicted. Cu core Au shell configurations are predicted in Cu–Au clusters. In Ag–Au clusters, most Ag atoms are on the surface, but partial ones are located in the inner shell, while Au atoms are interconnected in the middle shell.

The Melting Behaviors of the Bimetallic Cluster ConCu55-n(n=0~55)

The melting behaviors of ConCu55-n(n=0~55) bimetallic cluster were studied by using semi-empirical Gupta potential combined with molecular dynamics simulations. The melting point of the ConCu55-n(n=0~55) cluster shows itself the trend of going up, accompanied by the increasing of the Cobalt atomicity. However, it is between Co55 and Cu55 elementary cluster for melting point overall. Meanwhile the variation in the width of pre-melting temperature is greater, if around n0 or n55, but it is lesser nearly n55/2(namely Co and Cu at the same atomicity). In addition, the saturation point of specific heat capacity can be determined corresponding to the peak of Lindemann index.

Formation of Defects by Stretching Gold Nanosheet - A Simulation Study

Under tensile deformation, gold nanosheets elongate to form defects via a series of small vacancies leading to structural deformations. Behavior of finite gold nanosheets containing 57 and 73 atoms under load are investigated modeled by many-body Gupta potential. Nanosheets with close packed structure (111) plane of a face-centered-cubic structure are stretched along one of the two symmetry directions of the plane. The accessibility of these structures and their stability under load are found to be the key factors governing the morphological evolution of the gold nanosheets. It is found that major deformation is the formation of vacancies which could be called defects in the sheets and is surprisingly different from the ultimate stretching of a nanocylinder which is via neck formation. Thus this study presents completely new theoretical results for gold nanosheets.