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git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@5018 f3b2605a-c512-4ea7-a41b-209d697bcdaa

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sjplimp
2010-10-11 17:03:34 +00:00
parent 50fb5e430b
commit 1f68ebab80
2 changed files with 36 additions and 8 deletions
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22
doc/fix_nh.html
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@ -93,12 +93,19 @@ a bias velocity removed before thermostatting takes place; see the
description below. The desired temperature at each timestep is a
ramped value during the run from <I>Tstart</I> to <I>Tstop</I>. The <I>Tdamp</I>
parameter is specified in time units and determines how rapidly the
temperature is relaxed. For example, a value of 100.0 means to relax
the temperature in a timespan of (roughly) 100 time units (tau or
temperature is relaxed. For example, a value of 10.0 means to relax
the temperature in a timespan of (roughly) 10 time units (e.g. tau or
fmsec or psec - see the <A HREF = "units.html">units</A> command). The atoms in the
fix group are the only ones whose velocities and positions are updated
by the velocity/position update portion of the integration.
</P>
<P>IMPORTANT NOTE: A Nose-Hoover thermostat will not work well for
arbitrary values of <I>Tdamp</I>. If <I>Tdamp</I> is too small, the temperature
can fluctuate wildly; if it is too large, the temperature will take a
very long time to equilibrate. A good choice for many models is a
<I>Tdamp</I> of around 100 timesteps. Note that this is NOT the same as
100 time units for most <A HREF = "units.html">units</A> settings.
</P>
<HR>
<P>The barostat for fix styles <I>npt</I> and <I>nph</I> is specified using one or
@ -137,10 +144,17 @@ simulation box must be triclinic, even if its initial tilt factors are
</P>
<P>For all barostat keywords, the <I>Pdamp</I> parameter operates like the
<I>Tdamp</I> parameter, determining the time scale on which pressure is
relaxed. For example, a value of 1000.0 means to relax the pressure
in a timespan of (roughly) 1000 time units (tau or fmsec or psec - see
relaxed. For example, a value of 10.0 means to relax the pressure in
a timespan of (roughly) 10 time units (e.g. tau or fmsec or psec - see
the <A HREF = "units.html">units</A> command).
</P>
<P>IMPORTANT NOTE: A Nose-Hoover barostat will not work well for
arbitrary values of <I>Pdamp</I>. If <I>Pdamp</I> is too small, the pressure
and volume can fluctuate wildly; if it is too large, the pressure will
take a very long time to equilibrate. A good choice for many models
is a <I>Pdamp</I> of around 1000 timesteps. Note that this is NOT the same
as 1000 time units for most <A HREF = "units.html">units</A> settings.
</P>
<P>Regardless of what atoms are in the fix group, a global pressure or
stress tensor is computed for all atoms. Similarly, when the size of
the simulation box is changed, all atoms are re-scaled to new

22
doc/fix_nh.txt
View File

@ -85,12 +85,19 @@ a bias velocity removed before thermostatting takes place; see the
description below. The desired temperature at each timestep is a
ramped value during the run from {Tstart} to {Tstop}. The {Tdamp}
parameter is specified in time units and determines how rapidly the
temperature is relaxed. For example, a value of 100.0 means to relax
the temperature in a timespan of (roughly) 100 time units (tau or
temperature is relaxed. For example, a value of 10.0 means to relax
the temperature in a timespan of (roughly) 10 time units (e.g. tau or
fmsec or psec - see the "units"_units.html command). The atoms in the
fix group are the only ones whose velocities and positions are updated
by the velocity/position update portion of the integration.
IMPORTANT NOTE: A Nose-Hoover thermostat will not work well for
arbitrary values of {Tdamp}. If {Tdamp} is too small, the temperature
can fluctuate wildly; if it is too large, the temperature will take a
very long time to equilibrate. A good choice for many models is a
{Tdamp} of around 100 timesteps. Note that this is NOT the same as
100 time units for most "units"_units.html settings.
:line
The barostat for fix styles {npt} and {nph} is specified using one or
@ -129,10 +136,17 @@ simulation box must be triclinic, even if its initial tilt factors are
For all barostat keywords, the {Pdamp} parameter operates like the
{Tdamp} parameter, determining the time scale on which pressure is
relaxed. For example, a value of 1000.0 means to relax the pressure
in a timespan of (roughly) 1000 time units (tau or fmsec or psec - see
relaxed. For example, a value of 10.0 means to relax the pressure in
a timespan of (roughly) 10 time units (e.g. tau or fmsec or psec - see
the "units"_units.html command).
IMPORTANT NOTE: A Nose-Hoover barostat will not work well for
arbitrary values of {Pdamp}. If {Pdamp} is too small, the pressure
and volume can fluctuate wildly; if it is too large, the pressure will
take a very long time to equilibrate. A good choice for many models
is a {Pdamp} of around 1000 timesteps. Note that this is NOT the same
as 1000 time units for most "units"_units.html settings.
Regardless of what atoms are in the fix group, a global pressure or
stress tensor is computed for all atoms. Similarly, when the size of
the simulation box is changed, all atoms are re-scaled to new