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rLAMMPS lammps
compute_temp_region.html
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<HTML>
<CENTER><A
HREF =
"http://lammps.sandia.gov"
>
LAMMPS WWW Site
</A>
-
<A
HREF =
"Manual.html"
>
LAMMPS Documentation
</A>
-
<A
HREF =
"Section_commands.html#comm"
>
LAMMPS Commands
</A>
</CENTER>
<HR>
<H3>
compute temp/region command
</H3>
<P><B>
Syntax:
</B>
</P>
<PRE>
compute ID group-ID temp/region region-ID
</PRE>
<UL><LI>
ID, group-ID are documented in
<A
HREF =
"compute.html"
>
compute
</A>
command
<LI>
temp/region = style name of this compute command
<LI>
region-ID = ID of region to use for choosing atoms
</UL>
<P><B>
Examples:
</B>
</P>
<PRE>
temperature mine flow region boundary
</PRE>
<P><B>
Description:
</B>
</P>
<P>
Define a computation that calculates the temperature of a group of
atoms in a geometric region. This can be useful for thermostatting
one portion of the simulation box. E.g. a McDLT simulation where one
side is cooled, and the other side is heated. A compute of this style
can be used by any command that computes a temperature,
e.g.
<A
HREF =
"thermo_modify.html"
>
thermo_modify
</A>
,
<A
HREF =
"fix_temp_rescale.html"
>
fix
temp/rescale
</A>
, etc.
</P>
<P>
Note that a
<I>
region
</I>
-style temperature can be used to thermostat with
<A
HREF =
"fix_temp_rescale.html"
>
fix temp/rescale
</A>
or
<A
HREF =
"fix_langevin.html"
>
fix
langevin
</A>
, but should probably not be used with
Nose/Hoover style fixes (
<A
HREF =
"fix_nvt.html"
>
fix nvt
</A>
,
<A
HREF =
"fix_npt.html"
>
fix
npt
</A>
, or
<A
HREF =
"fix_nph.html"
>
fix nph
</A>
), if the
degrees-of-freedom included in the computed T varies with time.
</P>
<P>
The temperature is calculated by the formula KE = dim/2 N k T, where
KE = total kinetic energy of the group of atoms (sum of 1/2 m v^2),
dim = 2 or 3 = dimensionality of the simulation, N = number of atoms
in both the group and region, k = Boltzmann constant, and T =
temperature.
</P>
<P>
A 6-component kinetic energy tensor is also calculated by this compute
for use in the computation of a pressure tensor. The formula for the
components of the tensor is the same as the above formula, except that
v^2 is replaced by vx * vy for the xy component, etc.
</P>
<P>
The number of atoms contributing to the temperature is compute each
time the temperature is evaluated since it is assumed atoms can
enter/leave the region. Thus there is no need to use the
<I>
dynamic
</I>
option of the
<A
HREF =
"compute_modify.html"
>
compute_modify
</A>
command for this
compute style.
</P>
<P>
Unlike other compute styles that calculate temperature, this compute
does NOT currently subtract out degrees-of-freedom due to fixes that
constrain molecular motion, such as
<A
HREF =
"fix_shake.html"
>
fix shake
</A>
and
<A
HREF =
"fix_rigid.html"
>
fix rigid
</A>
. If needed the subtracted
degrees-of-freedom can be altered using the
<I>
extra
</I>
option of the
<A
HREF =
"compute_modify.html"
>
compute_modify
</A>
command.
</P>
<P><B>
Restrictions:
</B>
none
</P>
<P><B>
Related commands:
</B>
</P>
<P><A
HREF =
"compute_temp.html"
>
compute temp
</A>
,
<A
HREF =
"compute_pressure.html"
>
compute
pressure
</A>
</P>
<P><B>
Default:
</B>
none
</P>
</HTML>
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