Molcular dynamics (MD) simulations and force fields are (and have been) a powerful tool to study many different systems, from small gas phase clusters to bulk simulations of proteins in water. However, a quantitative description is somewhat complicated due to the oversimplification of the molecular interactions that some force fields have, in which most cases they treat water as a rigid molecule, which prevents any kind spectroscopic analysis. During the last years, our lab has developed a set of extremely flexible potential energy functions (PEFs) based on the many-body expansion of the energy of a system, with explicit corrections at the one-body, two-body and three-body level through permutationally invariant polynomials (PIPs) fitted to reproduce CCSD(T) reference energies. These PEFs, which we call MB-nrg for many-body energy, although having CCSD(T) accuracy, have the computational cost of a polarizable force field. In this work, we show the development and application of the MB-nrg PEFs using two (soon public) software packages that allow to generate MB-nrg PEFs for any molecule, and use it to run many-body molecular dynamics (MB-MD) efficiently. We also show that when an accurate reference energy is used to fit the PIPs, the outcomes of the simulations are directly comparable with experiments. Although the size of the system that can be treated is relatively large (several thousand of molecules), the current methodology allows only to obtain MB-nrg PEFs for small molecules and molecular ions such as water and small organic solvents and ions. Future work will consist on expanding this same methodology to larger molecular systems.

MBX: Next generation molecular dynamics

2019 Fall National Meeting

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