Vibrational ground state properties of H5+ and its isotopomers from diffusion Monte Carlo calculations

Diffusion Monte Carlo computations, with and without importance sampling, of the zero-point properties of H-5(+) and its isotopomers using a recent high accuracy global potential energy surface are presented. The global minimum of the potential possesses C-2v symmetry, but the calculations predict a D-2d geometry for zero-point averaged structure of H-5(+) with one H atom "in the middle" between two HH diatoms. The predicted zero-point geometries of the deuterated forms have H in the middle preferred over D in the middle and for a nonsymmetric arrangement of D atoms the preferred arrangement is one which maximizes the number of D as the triatomic ion. We speculate on the consequences of these preferences in scattering of H-2+H-3(+) and isotopomers at low energies, such as those in the interstellar medium. (c) 2008 American Institute of Physics.