### Abstract

Typically, the most time consuming part of any atomistic molecular simulation is the repeated calculation of distances, energies, and forces between pairs of atoms. However, many molecules contain nearly rigid multi-atom groups such as rings and other conjugated moieties, whose rigidity can be exploited to significantly speed-up computations. The availability of GB-scale random-access memory (RAM) offers the possibility of tabulation (precalculation) of distance- and orientation-dependent interactions among such rigid molecular bodies. Here, we perform an investigation of this energy tabulation approach for a fluid of atomistica-but rigida-benzene molecules at standard temperature and density. In particular, using O(1) GB of RAM, we construct an energy look-up table, which encompasses the full range of allowed relative positions and orientations between a pair of whole molecules. We obtain a hardware-dependent speed-up of a factor of 24-50 as compared to an ordinary ("exact") Monte Carlo simulation and find excellent agreement between energetic and structural properties. Second, we examine the somewhat reduced fidelity of results obtained using energy tables based on much less memory use. Third, the energy table serves as a convenient platform to explore potential energy smoothing techniques, akin to coarse-graining. Simulations with smoothed tables exhibit near atomistic accuracy while increasing diffusivity. The combined speed-up in sampling from tabulation and smoothing exceeds a factor of 100. For future applications, greater speed-ups can be expected for larger rigid groups, such as those found in biomolecules.

Original language | English (US) |
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Pages (from-to) | 268-275 |

Number of pages | 8 |

Journal | Journal of Computational Chemistry |

Volume | 33 |

Issue number | 3 |

DOIs | |

State | Published - Jan 30 2012 |

### Keywords

- accelerated Monte Carlo
- benzene fluid simulation
- distance and orientation dependent energy table
- energy look-up table
- look-up table speed-up
- molecular Monte Carlo
- potential energy smoothing
- precalculated energies between rigid bodies
- rigid body atomistic fluids

### ASJC Scopus subject areas

- Chemistry(all)
- Computational Mathematics