.. index:: compute_modify

compute_modify command
======================

Syntax
""""""

.. parsed-literal::

   compute_modify compute-ID keyword value ...

* compute-ID = ID of the compute to modify
* one or more keyword/value pairs may be listed
* keyword = *extra* or *dynamic*
.. parsed-literal::

     *extra* value = N
       N = # of extra degrees of freedom to subtract
     *dynamic* value = *yes* or *no*
       yes/no = do or do not recompute the number of atoms contributing to the temperature
     *thermo* value = *yes* or *no*
       yes/no = do or do not add contributions from fixes to the potential energy



Examples
""""""""

.. parsed-literal::

   compute_modify myTemp extra 0
   compute_modify newtemp dynamic yes extra 600

Description
"""""""""""

Modify one or more parameters of a previously defined compute.  Not
all compute styles support all parameters.

The *extra* keyword refers to how many degrees-of-freedom are
subtracted (typically from 3N) as a normalizing factor in a
temperature computation.  Only computes that compute a temperature use
this option.  The default is 2 or 3 for :doc:`2d or 3d systems <dimension>` which is a correction factor for an ensemble
of velocities with zero total linear momentum.  You can use a negative
number for the *extra* parameter if you need to add
degrees-of-freedom.  See the :doc:`compute temp/asphere <compute_temp_asphere>` command for an example.

The *dynamic* keyword determines whether the number of atoms N in the
compute group is re-computed each time a temperature is computed.
Only compute styles that compute a temperature use this option.  By
default, N is assumed to be constant.  If you are adding atoms to the
system (see the :doc:`fix pour <fix_pour>` or :doc:`fix deposit <fix_deposit>` commands) or expect atoms to be lost
(e.g. due to evaporation), then this option can be used to insure the
temperature is correctly normalized.

The *thermo* keyword determines whether the potential energy
contribution calculated by some :doc:`fixes <fix>` is added to the
potential energy calculated by the compute.  Currently, only the
compute of style *pe* uses this option.  See the doc pages for
:doc:`individual fixes <fix>` for details.

Restrictions
""""""""""""
 none

Related commands
""""""""""""""""

:doc:`compute <compute>`

Default
"""""""

The option defaults are extra = 2 or 3 for 2d or 3d systems and
dynamic = no.  Thermo is *yes* if the compute of style *pe* was
defined with no extra keywords; otherwise it is *no*.


.. _liws: http://www.cfdem.com
.. _ld: Manual.html
.. _lc: Section_commands.html#comm