Preliminary density functional calculations on the formic acid dimer

Abstract

The utility of density functional theory (DFT) to simulate the energetics of intermolecular rearrangement, dissociation energy, and, as well as the fine topological features of the molecular charge distribution has been tested for the formic acid dimer. The equilibrium and transition state structures are optimized using adiabatic connection method (ACM) and the barriers to the double proton transfer reaction have been also evaluated. The ACM results are compared with those obtained from SCF, MP2 and various DFT functionals. Preliminary results indicate that there is perhaps a significant role of the correlation effects in determining the barrier height for this reaction. The formic acid dimer dissociation energies calculated from the non-local gradient corrected or ACM functionals are in reasonable agreement with experimental estimates. Comparison of the DFT, SCF and MP2 electrostatic molecular potentials derived from cumulative atomic multipole moments (CAMM) for the formic acid dimer indicates that the correlation effects are reproduced correctly, providing that DFT atomic charges are supplemented by higher atomic multipole moments.