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git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@2933 f3b2605a-c512-4ea7-a41b-209d697bcdaa

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sjplimp
2009-06-30 22:51:36 +00:00
parent 87c330d436
commit b58c43a5ec
2 changed files with 14 additions and 4 deletions
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9
doc/fix_viscous.html
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@ -57,6 +57,11 @@ optional keyword <I>scale</I> is used, gamma can scaled up or down by the
specified factor for atoms of that type. It can be used multiple specified factor for atoms of that type. It can be used multiple
times to adjust gamma for several atom types. times to adjust gamma for several atom types.
</P> </P>
<P>IMPORTANT NOTE: You should specify gamma in force/velocity units.
This is not the same as mass/time units, at least for some of the
LAMMPS <A HREF = "units.html">units</A> options like "real" or "metal" that are not
self-consistent.
</P>
<P>In a Brownian dynamics context, gamma = kT / D, where k = Boltzmann's <P>In a Brownian dynamics context, gamma = kT / D, where k = Boltzmann's
constant, T = temperature, and D = particle diffusion coefficient. D constant, T = temperature, and D = particle diffusion coefficient. D
can be written as kT / (3 pi eta d), where eta = dynamic viscosity of can be written as kT / (3 pi eta d), where eta = dynamic viscosity of
@ -76,8 +81,8 @@ viscous damping term as fix viscous and adds a random force to each
atom. Hence if using fix <I>langevin</I> you do not typically need to use atom. Hence if using fix <I>langevin</I> you do not typically need to use
fix <I>viscous</I>. Also note that the gamma of fix viscous is related to fix <I>viscous</I>. Also note that the gamma of fix viscous is related to
the damping parameter of <A HREF = "fix_langevin.html">fix langevin</A>, except that the damping parameter of <A HREF = "fix_langevin.html">fix langevin</A>, except that
the units of gamma are force/velocity (or mass/time) and the units of the units of gamma are force/velocity and the units of damp are time,
damp are time, so that it can more easily be used as a thermostat. so that it can more easily be used as a thermostat.
</P> </P>
<P><B>Restart, fix_modify, output, run start/stop, minimize info:</B> <P><B>Restart, fix_modify, output, run start/stop, minimize info:</B>
</P> </P>

9
doc/fix_viscous.txt
View File

@ -47,6 +47,11 @@ optional keyword {scale} is used, gamma can scaled up or down by the
specified factor for atoms of that type. It can be used multiple specified factor for atoms of that type. It can be used multiple
times to adjust gamma for several atom types. times to adjust gamma for several atom types.
IMPORTANT NOTE: You should specify gamma in force/velocity units.
This is not the same as mass/time units, at least for some of the
LAMMPS "units"_units.html options like "real" or "metal" that are not
self-consistent.
In a Brownian dynamics context, gamma = kT / D, where k = Boltzmann's In a Brownian dynamics context, gamma = kT / D, where k = Boltzmann's
constant, T = temperature, and D = particle diffusion coefficient. D constant, T = temperature, and D = particle diffusion coefficient. D
can be written as kT / (3 pi eta d), where eta = dynamic viscosity of can be written as kT / (3 pi eta d), where eta = dynamic viscosity of
@ -66,8 +71,8 @@ viscous damping term as fix viscous and adds a random force to each
atom. Hence if using fix {langevin} you do not typically need to use atom. Hence if using fix {langevin} you do not typically need to use
fix {viscous}. Also note that the gamma of fix viscous is related to fix {viscous}. Also note that the gamma of fix viscous is related to
the damping parameter of "fix langevin"_fix_langevin.html, except that the damping parameter of "fix langevin"_fix_langevin.html, except that
the units of gamma are force/velocity (or mass/time) and the units of the units of gamma are force/velocity and the units of damp are time,
damp are time, so that it can more easily be used as a thermostat. so that it can more easily be used as a thermostat.
[Restart, fix_modify, output, run start/stop, minimize info:] [Restart, fix_modify, output, run start/stop, minimize info:]