Energetics, geometries and vibrational frequencies of three minimum energy structures of the HF2--(H2O)(2) Complex 2 are examined using density functional theory. For the most stable geometry the water molecules are hydrogen bonded to different F atoms of HF2- and to one another, forming a ring structure, and the water dimer is largely intact. Both the F-F distance and the blue shift of the F-H-F asymmetric stretch are significantly smaller than for HF2--H2O. The energy for dissociation to HF + F--(H2O)(2) is 27.1 kcal/mol, and the strong hydrogen bond of HF- is weakened by 2 18.9 kcal/mol (41%). (C) 2002 Elsevier Science B.V. All rights reserved.