Potassium(I) in water from Theoretical Calculations

Abstract The optimized geometry and energy for [K(H2O)n=1-8] + clusters have been studied using different basis sets and different methods (HF, MP2(FULL), BLYP and B3LYP). Moreover, two analytical potentials have been developed for potassium in water based on MP2(FULL) and B3LYP computations using the 6-311g * for potassium and the aug-cc-pVTZ(H2O) basis set for water. Two molecular dynamics simulations have been performed using the potentials, separately, together with a polarizable water potential. The simulation using both models show that the local water structure in both the first and second solvation shell of the ion is flexible. The distribution of the coordination numbers for both the models is wide (5-12) and the average coordination number higher for the model based on the MP2(FULL) calculations (8.1) than for the model based on B3LYP calculations (6.5). This difference can mostly be explained by differences in K +-(H2O)n binding energies for the two methods, as well as the fact that the water model was developed using MP2. “If it is true that every theory must be based upon observed facts, it is equally true that facts can not be observed without the guidance of some theory. Without such guidance, our facts would be desultory and fruitless; we could not retain them: for the most part we could not even perceive them.