| Abstract
| - An extensive liquid simulation study combining Monte Carlo and molecular dynamics techniques wasperformed for liquid formic acid. We investigated thermodynamic, dynamic, and spectroscopic properties ofthe liquid. The examination of several dynamic properties leads to a detailed picture of the molecularcontributions to the macroscopic properties of the liquid phase. Although the present model overestimatesthe diffusion constant by about 25%, the calculated spectral densities for the translational and rotational modesof the solvent in combination with ab initio calculated harmonic frequencies provide a valuable tool in thequalitative assignment of several important features of the low-frequency liquid phase Raman spectrum. Therelaxation time scales also give reasonably good agreement with dielectric relaxation and NMR measurements.Hydrogen-bonding dynamics provide interesting additional information on the dynamical time scales. Theaverage lifetime of the strongest types of hydrogen bonds is less than 0.5 ps. The relative population of thedimers with two hydrogen bonds undergoes a significant change relative to the gas phase population, theweight of the less stable dimers increasing substantially. Approximately 1% of the molecules participate inhydrogen-bonding patterns which dominate the crystalline phase of the formic acid. As an extension of thepresent work for the liquid phase, we have also performed calculations for the vapor−liquid equilibriumcoexistence curve predicting the critical temperature with 5% error. The application of the thermodynamicintegration method results in thermodynamic excess quantities as the excess free energy, entropy, and chemicalpotential.
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