Graduate Student Zachary Knepp

“Quantum Mechanically Derived Force Fields: An Automatable Approach for Simulating Molecules, Materials, Reactions, and More”

Have you ever wondered how to simulate exotic systems such as supramolecular or transition metal complexes? How about something as complicated as Metal-Organic Frameworks? Simulating these systems generally requires ab initio (or quantum) molecular dynamics, because of their complex and dynamically evolving electronic structures. However, beyond a few atoms, ab initio molecular dynamics simulations are extremely computationally demanding and impractical. This is because the changing inter-atomic forces must be recalculated between each time step of the simulation, using density functional theory or some many-body wavefunction method. To overcome these limitations, a set of classical potential energy functions (i.e., stretching, bending, torsion, inversion, electrostatic, and non-covalent interactions) can be used to describe dynamic molecular behavior according to Newtonian mechanics.1 These functions, commonly referred to as force fields, are implemented in many molecular dynamics software packages, but are generally parametrized for small organic molecules and biomolecular systems.1,2 Unfortunately, these potentials must be reparametrized for systems beyond this subset of chemicals, if one wants to predict realistic chemical physics. Therefore, it would be convenient if this reparameterization process could be streamlined.
Several groups have elegantly automated the generation of quantum derived force fields and have introduced unique potentials to better predict the quantum behavior of molecules and materials.1-3 In this seminar, I will present the theoretical and methodological aspects of quantum mechanically derived force fields. A few examples of the automation procedure will be shared, and the method’s generally applicability will be revealed via results from molecular and condensed phase simulations.1-3 An extension to simulated chemical reactivity will be realized by the implementation of the empirical valence bond approach.4

References:
(1) Odinokov, A. et al. Exploiting the quantum mechanically derived force field for functional materials simulations. npj Comput Mater 7, 155 (2021)
(2) Grimme, S. A general quantum mechanically derived force field (QMDFF) for molecules and condensed phase simulations. J. Chem. Theor. Comput. 10, 4497–4514 (2014)
(3) Vanduyfhuys, L. et al. QuickFF: A Program for a Quick and Easy Derivation of Force Fields for Metal-Organic Frameworks From ab Initio input. Journal of Computational Chemistry, 36 (13), 1015–1027 (2015)
(4) Hartke, B., Grimme, S. Reactive force fields made simple. Phys. Chem. Chem. Phys, 17, 16715–16718 (2015)