ABSTRACT
Ab initio wave-function-based methods can predict intermolecular force fields very accurately for monomers containing a few atoms. These methods are, however, too time consuming for larger molecules, in particular for any molecules of biological interest or molecules forming energetic solid state materials. The density-functional theory (DFT) methods would be fast enough, but are currently not able to predict the very important dispersion component of the force field. A new perturbational method that is capable of computing the force fields accurately will be presented. This method is based on a DFT description of isolated molecules but computes intermolecular forces using expressions beyond DFT. Calculations for model compounds have shown that the new method reproduces all components of the intermolecular force, including dispersion, extremely well, in fact challenging the accuracy of wave-function-based methods. At the same time, the computer resources required by this method are similar to those of the standard DFT. The method has already been applied to interactions of two monomers containing 12 atoms each, and it should be able to handle interactions of molecules containing 20 and more atoms.
