Ab initio molecular dynamics of pseudorotating Li5

The geometry of the Li5 cluster has been optimized at the generalized valence bond (GVB) and complete active space self-consistent field (CASSCF) levels of theory utilizing ab initio molecular dynamics (AIMD) simulated annealing. The cluster is found to have a planar structure and pseudorotates on a time scale of picoseconds or faster at temperatures as low as 77 K. It is therefore quite likely that the pseudorotating Li5 cluster observed in prior EPR experiments at 77 K is planar, though it was originally suggested to be a trigonal bipyramid. Vibrational frequencies have also been calculated for the optimized structure and for the pseudorotation transition state.