Q-Chem is a state-of-the-art commercial quantum chemistry program that is used to model atomic and molecular processes over a wide range of disciplines, including biology, chemistry, and materials science. Among the quantum chemistry methods, density functional theory (DFT) is perhaps the most widely used, especially in molecular biology, due to its ability to accurately model a wide range of molecular systems with reasonable computational cost. Still, DFT does not include the dispersion correlation effect, or van der Waals interaction, which plays a critical role in the determination of the overall conformations of molecular systems and accordingly, is indispensable in the study of DNA and proteins, molecular recognition, the packing of crystals, etc. We propose to add the ability to accurately model dispersion effects within the DFT framework. Specifically, we will develop and implement self-consistent-field (SCF) and gradient solutions to a recently proposed dispersion model, which has been shown to yield very accurate dispersion coefficients for R-6 and higher order terms with no empirical parameters, and very accurate binding energies for weakly bound systems and relative conformation energies with a damping term of just two empirical parameters. Currently this model cannot be applied in practical studies because it can only be used to calculate molecular energies due to the lack of SCF and gradient algorithms. The successful development and implementation of the model will lead to much more reliable DFT solutions for real chemical and biological problems. ? ?
This project aims to develop and implement a very accurate DFT method. DFT is at the core of molecular modeling and is applied widely in biological research/development and in drug discovery. The improved DFT will significantly increase researchers' quality of work and extend the application scope of DFT. ? ? ?
