Vibrational frequencies of (H2O) n and (D2O) n clusters for n = 2 and 8: possible relevance to inelastic neutron scattering of ice

Hartree-Fock plus MP2 corrections are reported for the vibrational frequencies in (H₂O)₂ and (D₂O)₂ and in the cubic octamers (H₂O)₈ and (D₂O)₈. The motivation was the inelastic incoherent neutron scattering of ice as studied experimentally by Li et al. (J.-C. Li, D. Londono, D.K. Ross, J.L. Finney, S.M. Bennington and A.D. Taylor (1992). J. Phys. Cond. Matter, 4, 2109). Some contact is made between our results and these experiments, and also with earlier infrared and Raman studies of Bertie and coworkers.