TY - JOUR

T1 - Modified nonequilibrium molecular dynamics for fluid flows with energy conservation

AU - Tuckerman, Mark E.

AU - Mundy, Christopher J.

AU - Balasubramanian, Sundaram

AU - Klein, Michael L.

PY - 1997/4/1

Y1 - 1997/4/1

N2 - The nonequilibrium molecular dynamics generated by the SLLOD algorithm [so called due to its association with the DOLLS tensor algorithm (D. J. Evans and G. P. Morriss, Statistical Mechanics of Nonequilibrium Liquids (Academic, New York, 1990)] for fluid flow is considered. It is shown that, in the absence of time-dependent boundary conditions (e.g., shearing boundary conditions via explicit cell dynamics or Lees-Edwards boundary conditions), a conserved energy, H′ exists for the equations of motion. The phase space distribution generated by SLLOD dynamics can be explicitly derived from H′. In the case of a fluid confined between two immobile boundaries undergoing planar Couette flow, the phase space distribution predicts a linear velocity profile, a fact which suggests the flow is field driven rather than boundary driven. For a general flow in the absence of time-dependent boundaries, it is shown that the SLLOD equations are no longer canonical in the laboratory momenta, and a modified form of the SLLOD dynamics is presented which is valid arbitrarily far from equilibrium for boundary conditions appropriate to the flow. From an analysis of the conserved energy for the new SLLOD equations in the absence of time-dependent boundary conditions, it is shown that the correct local thermodynamics is obtained. In addition, the idea of coupling each degree of freedom in the system to a Nosé-Hoover chain thermostat is presented as a means of efficiently generating the phase space distribution.

AB - The nonequilibrium molecular dynamics generated by the SLLOD algorithm [so called due to its association with the DOLLS tensor algorithm (D. J. Evans and G. P. Morriss, Statistical Mechanics of Nonequilibrium Liquids (Academic, New York, 1990)] for fluid flow is considered. It is shown that, in the absence of time-dependent boundary conditions (e.g., shearing boundary conditions via explicit cell dynamics or Lees-Edwards boundary conditions), a conserved energy, H′ exists for the equations of motion. The phase space distribution generated by SLLOD dynamics can be explicitly derived from H′. In the case of a fluid confined between two immobile boundaries undergoing planar Couette flow, the phase space distribution predicts a linear velocity profile, a fact which suggests the flow is field driven rather than boundary driven. For a general flow in the absence of time-dependent boundaries, it is shown that the SLLOD equations are no longer canonical in the laboratory momenta, and a modified form of the SLLOD dynamics is presented which is valid arbitrarily far from equilibrium for boundary conditions appropriate to the flow. From an analysis of the conserved energy for the new SLLOD equations in the absence of time-dependent boundary conditions, it is shown that the correct local thermodynamics is obtained. In addition, the idea of coupling each degree of freedom in the system to a Nosé-Hoover chain thermostat is presented as a means of efficiently generating the phase space distribution.

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U2 - 10.1063/1.473582

DO - 10.1063/1.473582

M3 - Article

AN - SCOPUS:0000225760

VL - 106

SP - 5615

EP - 5621

JO - Journal of Chemical Physics

JF - Journal of Chemical Physics

SN - 0021-9606

IS - 13

ER -