Structuring molecular hydrogen around ionic dopants: Li+ cations in small pH(2) clusters

The formation of clusters of molecular hydrogen around a cationic charge, the Li+ ion, is modelled by treating the global interaction as a sum of potentials where the Li+-H-2 forces come from a full anisotropic potential energy surface produced earlier in our group. The H-2-H-2 interaction is taken from the literature and treated as a spherical potential between structureless bosonic solvent molecules of para-H-2 (pH(2)). The optimization of geometries and the minimum energy values are obtained via a genetic algorithm treatment whose structures are modified at the end to include a modelling of quantum effects. The results of hydrogen clustering around the cationic dopant indicate the presence of marked shell structures which are initially completed by the octahedral arrangement of the first six solvent partners, while the next shells are dominated by the mainly dispersive interaction among pH2 molecules and show, in larger clusters, less structured solvent collocations around the ionic impurity.