Journal Article Coupled Nosé-Hoover equations of motion to implement a fluctuating heat-bath temperature

Moritsugu, Kei  ,  Fukuda, Ikuo

93 ( 3 )  , p.033306 , 2015-08-18
The Nosé-Hoover equation provides a universal and powerful protocol in computer simulation to realize an equilibrium canonical temperature for a target physical system, and thus fruitful gains are expected in the utility if plural Nosé-Hoover equations are suitably coupled. Here, to realize a nonequilibrium temperature, we present coupled Nosé-Hoover equations in which the physical system and a temperature system are dynamically coupled. The temperature fluctuations generated by this newly defined temperature system are not ad hoc, and their statistical distribution is completely described. This allows sampling of the physical system that develops at the nonequilibrium temperature. Since the total system is governed by a prescribed distribution, the equilibrium of the physical system is also reconstructed by reweighting. We provide a scheme for setting the distribution of the dynamical inverse temperature as well as statistical relationship between dynamical and physical temperatures. The statistical and dynamical features and the sampling abilities of the current method were demonstrated via distributions, trajectories, dynamical correlations, and free energy landscapes for a model system and a biomolecular system. Our coupled Nosé-Hoover scheme works well, and allows a physical system to be simulated in a nonequilibrium-temperature heat bath with both statistical and arbitrary definitions, which will also facilitate applications to enhanced sampling of physical systems in equilibrium.

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