Many-body interactions calculated with the direct reaction field model Original Research Article

The direct reaction field (DRF) model was developed for calculations of electronic properties of molecules in the condensed phase. In the DRF approach the electrons of (part(s) of a system is described with wavefunctions, the larger parts classically with point charges and polarizabilities. Leaving out the quantum-mechanical part(s) leads naturally to a polarizable force field. In this paper we demonstrate the usefulness of the DRF model for the study of many-body interactions in polar systems. We have calculated the many-body interactions in clusters of HF, H2O and urea in our classical polarization model and compared the results to ab initio calculations using large basis sets. We find that the results obtained using the classical model compare excellently to ab initio results.