Accurate computation of shear viscosity from equilibrium molecular dynamics simulations

نویسندگان

  • D. Nevins
  • F. J. SPERA
چکیده

This article may be used for research, teaching and private study purposes. Any substantial or systematic reproduction, redistribution , reselling , loan or sub-licensing, systematic supply or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material. The accuracy of the Green – Kubo formulation for computing shear viscosity from equilibrium molecular dynamics simulations depends on the quality of the potential and on how the viscosity computation is carried out. We examine the role of the duration of the simulation, the number of particles used, and how the correlations are accumulated on the accuracy of the computed viscosity. We propose as a measure of the accuracy the standard deviation of five independently computed shear viscosity values based on independent components of the stress tensor. Using this measure, we examine the shear viscosity calculation for molten NaCl to determine the values of the run length, window width, and spacing between windows and obtain a good compromise between calculation time and viscosity quality. Significantly we note that even though viscosity can be calculated using relatively few particles, reducing state point uncertainty requires more, rather than less, particles.

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تاریخ انتشار 2008