Electrostatic Domination of the Effect of Electron Correlation in Intermolecular Interactions.
The electron-electron correlation energy is negative, and attractive dispersion interactions are entirely a correlation effect; therefore, the contribution of correlation to intermolecular binding is commonly assumed to be negative, or binding in nature. However, there are many cases where the long-range correlation binding energy is positive, with certain geometries of the water dimer as a prominent example. Geometries with dipoles misaligned can also have an electrostatically dominated, though negative, long-range correlation binding. In either case, the interaction decays as R(-3). This has its origin in the systematic overestimation of dipole moments by Hartree-Fock theory, leading to a reduction in the calculated electrostatic attraction upon inclusion of correlation. Thus, energy decomposition analyses that include correlation but do not correct mean field electrostatic terms are suboptimal. Attenuated second-order Møller-Plesset theory, which smoothly truncates long-range electron correlation effects to zero, can, paradoxically, have the correct long-range behavior for many intermolecular interactions.
Kenneth S. Pitzer Center for Theoretical Chemistry, Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States.|Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
Jonathan
J
Thirman
Kenneth S. Pitzer Center for Theoretical Chemistry, Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States.|Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
Martin
M
Head-Gordon
ab initio calculations; electron correlation; energy decomposition analysis; intermolecular interactions; water dimer