A density-functional theory including dispersion interactions
Johnson, Erin R.
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The London dispersion interaction is responsible for attraction between non-polar molecules and is of great importance in describing structure and reactivity in many areas of chemistry. Dispersion is difficult to model accurately. Density Functional Theory (DFT) methods, widely used in computational chemistry today, do not include the necessary physics. This often leads to qualitatively incorrect predictions when DFT is applied to dispersion-bound systems. A novel DFT method has been developed which is capable of accurately modeling dispersion. Dispersion attraction between molecules arises when an instantaneous dipole moment in one molecule induces a dipole moment in a second molecule. Our approach proposes that the source of these instantaneous dipole moments is the position-dependent dipole moment of the exchange hole. The model is no more computationally expensive than existing DFTs and gives remarkably accurate dispersion coefficients, intermolecular separations, intermolecular binding energies, and intramolecular conformational energies. Our dispersion theory is also combined with previous post-exact-exchange models of dynamical and nondynamical correlation, yielding a unified exact-exchange-based energy functional called DF07. DF07 overcomes many of the outstanding problems in DFT arising from local exchange approximations. The DF07 model is shown to provide highly accurate results for thermochemistry, kinetics, and van der Waals interactions.