State point dependence of systematically coarse–grained potentials

Abstract

We apply systematic structural coarse–graining based on optimizing a potential against the structure obtained in atomistic simulations to the small organic glass former ortho-terphenyl (OTP). Atomistic radial distributions at various temperatures ranging from below the glass transition temperature to the equilibrium liquid show hardly any change with temperature. These pair distribution functions are used as targets to be reproduced by a mesoscale model of OTP which is formulated by replacing each benzene ring with a single interaction center. The potentials are obtained by Iterative Boltzmann Inversion of the distribution functions. The resulting potential depends not only on the structure but also implicitly on the temperature at which it was optimized. Potentials optimized in the liquid range lead to crystalline structures if used below the glass transition requiring independent optimizations in the glass. We compare potentials optimized in both ranges to study the system over the whole temperature range. The dynamic mapping turns out to be different for different mapping potentials.

Keywords:

• Molecular dynamics
• Coarse–graining
• Multiscale modeling
• Glasses
• Ortho-terphenyl
• Iterative Boltzmann inversion

Acknowledgements

This work was supported by the US Department of Energy, Office of Science, Office of Advanced Scientific Computing Research under Grant No. DE-FG02-03ER25568. This research also used resources of the National Energy Research Scientific Computing Center, which is supported by the Office of Science of the US Department of Energy under Contract No. DE-AC03-76SF00098.