(538b) Reactive Force Field Derived from First Principles

Atomic-level understanding and the bottom-up design of complex chemical reactions inherent to biomolecular and catalytic processes is currently hindered by the large computational burden of ab initio quantum mechanical methods, such as the density functional theory (DFT). Reactive force fields (ReaxFF, COMB, Tershoff, etc.) address this challenge through computationally efficient, albeit empirical, functional forms of the system’s potential energy as a function of atomic coordinates. Despite 30 years of development, such empirical chemical reactivity models still lack quantum mechanical rigor and suffer from transferability issues.¹

Herein, we propose a strategy to derive a reaction force field from first principles, by simplifying Kohn-Sham DFT equations through the application of the Weeks-Anderson-Davidson chemical pseudopotential theory.² We introduce an atomic potential approximation that leads to a physically transparent tight-binding model with non-empirical off-diagonal functional forms. The resulting method shows promising, and to some extent, unexpected accuracy and transferability for model molecules composed of Group 1 elements. A means to bypass the Hamiltonian matrix diagonalization is discussed, paving a way to a truly classical reactive force field.

References:

1. Senftle, T. P.; Hong, S.; Islam, M. M.; Kylasa, S. B.; Zheng, Y.; Shin, Y. K.; Junkermeier, C.; Engel-Herbert, R.; Janik, M. J.; Aktulga, H. M. "The ReaxFF reactive force-field: development, applications and future directions." Npj Computational Materials 2 (2016): 15011.
2. Weeks, J. D., P. W. Anderson, and A. G. H. Davidson. "Non‐Hermitian representations in localized orbital theories." The Journal of Chemical Physics 58.4 (1973): 1388-1395.