"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c

:link(lws,http://lammps.sandia.gov)
:link(ld,Manual.html)
:link(lc,Section_commands.html#comm)

:line

compute temp/ramp command :h3

[Syntax:]

compute ID group-ID temp/ramp vdim vlo vhi dim clo chi keyword value ... :pre

ID, group-ID are documented in "compute"_compute.html command
temp/ramp = style name of this compute command
vdim = {vx} or {vy} or {vz}
vlo,vhi = subtract velocities between vlo and vhi (velocity units)
dim = {x} or {y} or {z}
clo,chi = lower and upper bound of domain to subtract from (distance units)
zero or more keyword/value pairs may be appended to the args
keyword = {units} :ul
  {units} value = {lattice} or {box} :pre

[Examples:]

temperature 2nd middle ramp vx 0 8 y 2 12 units lattice :pre

[Description:]

Define a computation that calculates the temperature of a group of
atoms, while 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. "thermo_modify"_thermo_modify.html, "fix
temp/rescale"_fix_temp_rescale.html, "fix npt"_fix_npt.html, etc.

The meaning of the arguments for this command is the same as for the
"velocity"_velocity.html command which was presumably used to impose
the velocity.

The {units} keyword determines the meaning of the distance units used
for coordinates (c1,c2) and velocities (vlo,vhi).  A {box} value
selects standard distance units as defined by the "units"_units.html
command, e.g. Angstroms for units = real or metal.  A {lattice} value
means the distance units are in lattice spacings; e.g. velocity =
lattice spacings / tau.  The "lattice"_lattice.html command must have
been previously used to define the lattice spacing.

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.

The number of atoms contributing to the temperature is assumed to be
constant for the duration of the run; use the {dynamic} option of the
"compute_modify"_compute_modify.html command if this is not the case.

This compute subtracts out degrees-of-freedom due to fixes that
constrain molecular motion, such as "fix shake"_fix_shake.html and
"fix rigid"_fix_rigid.html.  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
{extra} option of the "compute_modify"_compute_modify.html command.

[Restrictions:] none

[Related commands:]

"compute temp"_compute_temp.html, "compute
temp/region"_compute_temp_region.html, "compute
pressure"_compute_pressure.html

[Default:]

The option default is units = lattice.