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compute_temp_ramp.html
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<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>
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<H3>compute temp/ramp command
</H3>
<P><B>Syntax:</B>
</P>
<PRE>compute ID group-ID temp/ramp vdim vlo vhi dim clo chi keyword value ...
</PRE>
<UL><LI>ID, group-ID are documented in <A HREF = "compute.html">compute</A> command
<LI>temp/ramp = style name of this compute command
<LI>vdim = <I>vx</I> or <I>vy</I> or <I>vz</I>
<LI>vlo,vhi = subtract velocities between vlo and vhi (velocity units)
<LI>dim = <I>x</I> or <I>y</I> or <I>z</I>
<LI>clo,chi = lower and upper bound of domain to subtract from (distance units)
<LI>zero or more keyword/value pairs may be appended to the args
<LI>keyword = <I>units</I>
</UL>
<PRE> <I>units</I> value = <I>lattice</I> or <I>box</I>
</PRE>
<P><B>Examples:</B>
</P>
<PRE>temperature 2nd middle ramp vx 0 8 y 2 12 units lattice
</PRE>
<P><B>Description:</B>
</P>
<P>Define a computation that calculates the temperature of a group of
atoms, after subtracting out an imposed velocity on the system before
computing the kinetic energy. 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>, <A HREF = "fix_npt.html">fix npt</A>, etc.
</P>
<P>The meaning of the arguments for this command is the same as for the
<A HREF = "velocity.html">velocity ramp</A> command which was presumably used to
impose the velocity.
</P>
<P>The <I>units</I> keyword determines the meaning of the distance units used
for coordinates (c1,c2) and velocities (vlo,vhi). A <I>box</I> value
selects standard distance units as defined by the <A HREF = "units.html">units</A>
command, e.g. Angstroms for units = real or metal. A <I>lattice</I> value
means the distance units are in lattice spacings; e.g. velocity =
lattice spacings / tau. The <A HREF = "lattice.html">lattice</A> command must have
been previously used to define the lattice spacing.
</P>
<P>A 6-component kinetic energy tensor is also calculated by this compute
for use in the calculation 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 assumed to be
constant for the duration of the run; use the <I>dynamic</I> option of the
<A HREF = "compute_modify.html">compute_modify</A> command if this is not the case.
</P>
<P>This compute subtracts 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>. This means the temperature of groups of
atoms that include these constraints will be computed correctly. 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_temp_region.html">compute
temp/region</A>, <A HREF = "compute_temp_deform.html">compute
temp/deform</A>, <A HREF = "compute_pressure.html">compute
pressure</A>
</P>
<P><B>Default:</B>
</P>
<P>The option default is units = lattice.
</P>
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