Please use this identifier to cite or link to this item: http://hdl.handle.net/2381/31940
Title: New Langevin and Gradient Thermostats for Rigid Body Dynamics
Authors: Davidchack, Ruslan L.
Ouldridge, T. E.
Tretyakov, M. V.
First Published: 18-Dec-2014
Citation: Journal of Chemical Physics, 2014, 142 : 144114
Abstract: We introduce two new thermostats, one of Langevin type and one of gradient (Brownian) type, for rigid body dynamics. We formulate rotation using the quaternion representation of angular coordinates; both thermostats preserve the unit length of quaternions. The Langevin thermostat also ensures that the conjugate angular momenta stay within the tangent space of the quaternion coordinates, as required by the Hamiltonian dynamics of rigid bodies. We have constructed three geometric numerical integrators for the Langevin thermostat and one for the gradient thermostat. The numerical integrators reflect key properties of the thermostats themselves. Namely, they all preserve the unit length of quaternions, automatically, without the need of a projection onto the unit sphere. The Langevin integrators also ensure that the angular momenta remain within the tangent space of the quaternion coordinates. The Langevin integrators are quasi-symplectic and of weak order two. The numerical method for the gradient thermostat is of weak order one. Its construction exploits ideas of Lie-group type integrators for differential equations on manifolds. We numerically compare the discretization errors of the Langevin integrators, as well as the efficiency of the gradient integrator compared to the Langevin ones when used in the simulation of rigid TIP4P water model with smoothly truncated electrostatic interactions. We observe that the gradient integrator is computationally less efficient than the Langevin integrators. We also compare the relative accuracy of the Langevin integrators in evaluating various static quantities and give recommendations as to the choice of an appropriate integrator.
DOI Link: 10.1063/1.4916312
Links: http://arxiv.org/abs/1412.5813v1
http://hdl.handle.net/2381/31940
http://scitation.aip.org/content/aip/journal/jcp/142/14/10.1063/1.4916312
Version: Post-print
Status: Peer-reviewed
Type: Journal Article
Rights: Copyright 2015 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Journal of Chemical Physics, 2014, 142 : 144114 and may be found at http://dx.doi.org/10.1063/1.4916312
Description: AMS 2000 subject classification. 65C30, 60H35, 60H10.
Appears in Collections:Published Articles, Dept. of Mathematics

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