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Re: [lammps-users] Diffusion Coefficient in 2D
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Re: [lammps-users] Diffusion Coefficient in 2D

From: Steve Plimpton <sjplimp@...24...>
Date: Thu, 22 Jun 2017 07:39:08 -0600

Since SRD particles do not interact with each other,
I don't think a VACF is meaningful.  Effectively
there are no velocity correlations.

When you say
MSD is incorrect, you can check yourself if
LAMMPS is producing a valid number.  Just output
one or more dump files and compute the MSD yourself
at some time delta.  I'm guessing you will find it
is the same.  What that means for an SRD fluid
and how to interpret it, is a different Q.


On Wed, Jun 21, 2017 at 5:40 PM, John Smith <johnson21smith@...36.....24...> wrote:

I have tried to modify the example script given under SRD to calculate vacf and mean squared displacement and I am attempting to calculate the diffusion coefficient from this. However, the values are not matching and the range is different. I also included the factors necessary for a 2D simulation (details given in examples/DIFFUSE) but this is still giving an incorrect result. I am attaching my input script as well as the output graphs. Please advice!


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