Theoretical study of the Na+Krn and NaKrn (n=1-25) small clusters

We have studied the structure and the stability of the ionic Na+Krn and neutral NaKrn (n= 1-25) small clusters. The potential energy surface of the cluster is described using additive potentials, which represent the pair interactions taken from the best available CCSD ab initio calculations. The VNa+Kr, VKr-Kr potentials have been fitted, respectively, by Tang and Toennies and Lennard-Jones (LJ) forms, while the V-NaKr is presented by a modified HFD analytical potential obtained by a fully quantum-mechanical approach based on very accurate spectroscopic data. In addition, the potential energy surface has been explored by the Monte Carlo Basin Hopping method in order to determine the geometry of Na+Krn and NaKrn clusters and their isomers. Their relative stability was studied by evaluating the energy per Krypton atom and the energy differences as function of number n of Krypton atoms in clusters. It was shown, for Na+Krn, that n = 6, 8, 10, 16 and 20 are the most stable structures, which is in good agreement with the previous experimental results. (C) 2009 Elsevier B.V. All rights reserved