CC-R12 calculations on the lowest stationary points of the H-5(+) energy surface

The four stationary points lowest in energy on the H-5(+) potential energy surface are studied at various levels of sophistication including CCSD(T)-R12 calculations. Absolute energies are obtained with errors less than 0.5 kJ mol(-1). Relative energies are supposed to be much more accurate. The binding energy (D-0) of H-5(+) with respect to H-3(+) and H-2 is 35.9 +/- 0.1 kJ mol(-1). The D-2d structure is a saddle point only similar to 0.8 kJ mol(-1) above two equivalent minima of C-2v symmetry.