Energy partitioning on intermolecular interactions: ab initio Monte Carlo study of water dimer

Ab initio Monte Carlo computations were carried out on H2O dimer system. By introducing the energy partitioning scheme that we have developed recently, ab initio calculated H2O-H2O interaction can be analyzed from the viewpoint of atom-atom interaction. The electronic polarization caused by the interaction and its temperature dependence are also discussed. To our best knowledge, this is the first report on the thermal distribution of electronic distortion energy assigned to a molecule.