Solvation of potassium cation in helium clusters: Density functional theory versus pairwise method.

Microsolvation of a cation in helium quantum solvent is an attractive phenomenon leading generally to the formation of a strongly packed structure known as 'Snowball' feature. Here, the lowest energy structures and the relative stability of the solvated potassium cation K in helium clusters KHe up to the size n = 20 are investigated employing Density Functional Theory (DFT) and pairwise methods. The DFT calculations showed that M05-2X/6-311++G (3df, 2p) level of theory can reproduce properly the experimental data of KHe diatomic potential, whereas, in the pairwise method, the Basin-Hopping Monte Carlo (BHMC) algorithm was applied for the global optimization.