THEORETICAL-STUDY OF WATER CLUSTERS .2. HEXAMER

Three water hexamer structures found with a 3-21G basis set molecular orbital optimization method were explored with the HF//6-311G* and HF/6-311G** basis sets. Thermodynamic quantities and IR and Raman spectra were calculated. With the larger basis set the differences in electronic energy, enthalpy, free energy and entropy between the chair form and the boat (prism) forms are 1.08 (- 0.84), 0.96 (- 0.84), 0.14 (3.67) kcal/mol, and 2.77 (- 13.21) cal/mol K. Calculations were also carried out for the ring and isosceles bipyramid configurations of the pentamer using the HF/6-311G* and MP2/6-311G* methods.