Ab initio molecular dynamics study on Agn (n=4, 5, 6)

Ab initio Molecular Dynamics (MD) method, based on density functional theory (DFT) with planewaves and pseudopotentials, was used to study the stability and internal motion in silver cluster Agn, with n = 4-6. Calculations on the neutral, cationic and anionic Silver dimer Ag-2 show that the bond distance and vibrational frequency calculated by DFT are of good duality. Simulations of Ag-4, Ag-5, and Ag-6: in canonical ensemble reveal distinct characteristics and isomerization paths for each cluster. At a temperature of 800 K, an Ag-4 has no definite structure due to internal motion, while for Ag-5, and Ag-6 the clusters maintain the planar structure, with atomic rearrangement observed for Ag-5 but not for Ags. At a temperature of 200 K, Ag-4 can exist in two planar structures whilst Ags is found to be stable only in the planar form. In contrast Age is stable in both planar trigonal and 3D pentagonal structures. Microcanonical MD simulation was performed for all three clusters to obtain the vibrational density of states (Dos).