科研之友
微信
新浪微博
Facebook
分享链接
摘要
Thermal fluctuations of a many-body system coupled to a Nose-Hoover thermostat depend on the strength of the coupling parameter tau*. A wrong choice may bring non-ergodic features and non-canonical fluctuations. Here, we analyse by means of molecular dynamics simulations both the energy fluctuations and the spectrum of the friction coefficient zeta(*) of an extended Lennard-Jones system in a wide range of tau* at liquid density. Three ranges of tau* are identified - small, intermediate and large, plus their transitions. For tau* values in the intermediate range, zeta(*) shows chaotic behaviour, and the particle system requires reasonable computing time for its thermalisation. As a result, the extended system is ergodic and energy fluctuations are canonical and stable in time. On the contrary, small and large ranges of tau* reveal clear evidence of periodicity in the thermostat variable, for instance by propagating the initial temperature condition. For these two ranges, the extended system shows non-ergodic features and energy fluctuations are non-canonical. For large tau*, micro-canonical fluctuations are occasionally obtained. For small to intermediate and intermediate to large ranges of tau*, the thermostat variable exhibits beat waves and is thus unable to reach equilibrium no matter how extended in time the simulations are. Here, we compare our results with previous work and explain the differences.
- 出版日期2015-5-3
