(449e) From Atomistic to Systematic Coarse-Grained Models for Molecular Systems Using Path-Space Methods

The development of systematic coarse-grained mesoscopic models for complex molecular systems is an intense research area. Here we give an overview of different methods for obtaining optimal parametrized coarse-grained models, starting from detailed atomistic representation for high dimensional molecular systems [1-4]. Methods such as inverse Monte Carlo, inverse Boltzmann, force matching, relative entropy, provide parameterizations of coarse-grained models at equilibrium by minimizing a fitting functional over a parameter space. All the methods mentioned in principle are employed to approximate a many body potential, the (n-body) potential of mean force, describing the equilibrium distribution of coarse grained sites observed in simulations of atomically detailed models.

Then, we further extend these studies using path-space methods (relative entropy rate) for coarse-graining and uncertainty quantification for non-equilibrium processes [2-3]. We provide systematic derivation of Langevin type coarse-grained dynamics from fine-scale molecular simulations, based on the minimization of the relative entropy rate. It is also shown that this minimization problem is equivalent to a weighted least squares problem, with weights that depend on the diffusion coefficient of the proposed stochastic dynamics for the coarse grained system.

We apply, and compare, the above described methodologies in several molecular systems: gas and fluid methane, water and a polymeric chain [3].

References:

[1] V. Harmandaris et al., Macromolecules, 39, 6708 (2006); Macromolecules, 42, 791 (2009); A. Rissanou, V. Harmandaris, Macromolecules, 48, 2761 (2015).

[2] E. Kalligiannaki, V. Harmandaris, M. Katsoulakis, P. Plechac, J. Chem. Phys., 143, 084105 (2015); V. Harmandaris, E. Kalligiannaki, M. Katsoulakis, P. Plechac, J. Comp. Phys., 314, 355 (2016).

[3] E. Kalligiannaki, A. Chazirakis, A. Tsourtis, M. Katsoulakis, P. Plechac, V. Harmandaris, Europ. Phys. J. Special Topics, 225, 1347 (2016).

[4] A. Tsourtis, V. Harmandaris, D. Tsagkarogiannis, Entropy, 19, 395 (2017).