 
Summary: Constraint method for deriving nonequilibrium molecular dynamics equations of motion
T. M. Galea and Phil Attard
Ian Wark Research Institute, University of South Australia, Mawson Lakes, South Australia 5095, Australia
Received 23 July 2002; published 24 October 2002
A procedure for developing nonHamiltonian equations of motion for constrained systems is given. It is
shown that such constraints can be used to mimic common statistical systems, both equilibrium e.g., constant
temperature and nonequilibrium e.g., shear flow, heat flow , and the procedure is suited for molecular
dynamics computer simulations. The method is demonstrated with isokinetic shear flow, in bulk and slit
geometries, which illustrates its flexibility. Results for the shear viscosity are in agreement with previously
published results.
DOI: 10.1103/PhysRevE.66.041207 PACS number s : 66.20. d, 02.70.Ns, 61.20.Ja, 61.20.Lc
I. INTRODUCTION
Molecular dynamics computer simulations are being used
to describe increasingly complex systems 1 . Originally re
stricted to a constant energy isolated system microcanonical
system molecular dynamics has since been used for constant
temperature 2 and constant pressure 3 equilibrium sys
tems, as well as in a variety of nonequilibrium applications
4 . Such embellishments necessarily invoke non
Hamiltonian equations of motion, and this raises fundamen
