STRUCTURES AND ENERGETICS OF PROTON-BOUND FORMIC ACID-WATER CLUSTERS,(HCOOH)(N)(H2O)H+

Semiempirical and ab initio calculations have been performed on proton -bound mixed clusters (HCOOH)(n)(H2O)H+ with n = 1-8. Energetically co mpetitive structures were deduced: open-chain structures with a H2O un it at the end are favored energetically for lower members (n < 4) of t he cluster series, nucleation around H3O+ begins at n = 4 and chains t erminated by cyclic dimer units with H3O+ at the center are favored fo r n = 5-8. Ring closure around H3O+ and dimer formation begins at n = 5. (C) 1997 Elsevier Science B.V.