Profile unbiased thermostat with dynamical streaming velocities

We have devised a reversible set of nonequilibrium molecular dynamics equations of motion to study viscous flow under an applied shear field utilizing a new profile unbiased thermostat: (PUT). Based on a modification of the original equations presented by Evans and Morriss [Phys. Rev. Lett. 56, 2172 (1986)], we have extended the phase space to include dynamically evolving streaming velocities. The new method is advantageous because it allows control of the rate at which the streaming velocities evolve and thereby removes the effects of high frequency thermal fluctuations. Further, in tests on a Weeks-Chandler-Andersen fluid, we find that a shear-induced microstructure, the so-called ''string phase,'' was not destabilized by the new PUT scheme. (C) 1996 American Institute of Physics.