Flying ice cube

2018-10-20T17:56:01Z

80.246.140.161: Fixed up page due to recent developments in the literature on the subject

The '''Flying ice cube''' <ref>[http://www3.interscience.wiley.com/journal/33911/abstract Stephen C. Harvey, Robert K.-Z. Tan, Thomas E. Cheatham III "The flying ice cube: Velocity rescaling in molecular dynamics leads to violation of energy equipartition", Journal of Computational Chemistry '''19''' pp. 726-740 (1998)]</ref>
is an artificial situation encountered in [[ molecular dynamics]] simulations whereby an incorrect [[equipartition]] of energy is brought about
by [[Thermostats| thermostats]] that improperly implement some form of periodic velocity rescaling outside of the continuous equations of motion, such as the [[Berendsen thermostat]].
The artifact is due to these thermostats violating the balance condition that is a requirement of Monte Carlo simulations ([[ molecular dynamics ]] simulations with velocity rescaling thermostats can be thought of as Monte Carlo simulations with [[ molecular dynamics]] moves and velocity rescaling moves).<ref name="Braun et al">[http://doi.org/10.1021/acs.jctc.8b00446 Efrem Braun, Seyed M. Moosavi, Berend Smit "Anomalous Effects of Velocity Rescaling Algorithms: The Flying Ice Cube Effect Revisited", Journal of Chemical Theory and Computation '''14''' pp. 5262-5272 (2018)]</ref>
The net result is that an instability forms where the kinetic energy may be drained from some [[Degree of freedom| degrees of freedom]] and be incorrectly fed into others. A manifestation of this would be the kinetic energy from the high frequency bond vibrations and angle bending in a system composed of, say, flexible [[Water models|water molecules]] ending up in the zero frequency mode of the kinetic energy of the system as a whole (''i.e.'' centre of mass translation); the molecular motions would become frozen, resulting in a ''flying ice cube''. Note that despite the name, this situation is not limited to simulations of water.
This artifact is avoided by using a velocity rescaling thermostat that obeys the balance condition, such as the [[Bussi-Donadio-Parrinello thermostat]].<ref name="Braun et al"/>
==References==
<references/>
;
[[category: molecular dynamics]]

SklogWiki - User contributions [en]

Flying ice cube