In search of CS2(H2O)(n=1-4) clusters

摘要

Gaussian-3 and MP2/aug-cc-pVnZ methods have been used to calculate geometries and thermochemistry of CS2(H2O)(n), where n=1-4. An extensive molecular dynamics search followed by optimization using these two methods located two dimers, six trimers, six tetramers, and two pentamers. The MP2/aug-cc-pVDZ structure matched best with the experimental result for the CS2(H2O) dimer, showing that diffuse functions are necessary to model the interactions found in this complex. For larger CS2(H2O)(n) clusters, the MP2/aug-cc-pVDZ minima are significantly different from the MP2(full)/6-31G(*) structures, revealing that the G3 model chemistry is not suitable for investigation of sulfur containing van der Waals complexes. Based on the MP2/aug-cc-pVTZ free energies, the concentration of saturated water in the atmosphere and the average amount of CS2 in the atmosphere, the concentrations of these clusters are predicted to be on the order of 10(5) CS2(H2O) clusters center dot cm(-3) and 10(2) CS2(H2O)(2) clusters center dot cm(-3) at 298.15 K. The MP2/aug-cc-pVDZ scaled harmonic and anharmonic frequencies of the most abundant dimer cluster at 298 K are presented, along with the MP2/aug-cc-pVDZ scaled harmonic frequencies for the CS2(H2O)(n) structures predicted to be present in a low-temperature molecular beam experiment. (c) 2007 American Institute of Physics.