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small tweaks to align fix numdiff with the rest of the manual

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Axel Kohlmeyer 2020-03-18 23:04:02 -04:00
parent b4919756d4
commit 72b70a041d
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1 changed files with 10 additions and 16 deletions
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26
doc/src/fix_numdiff.rst
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@ -6,22 +6,19 @@ fix numdiff command
Syntax
""""""
.. parsed-literal::
fix ID group-ID numdiff Nevery Delta
fix ID group-ID numdiff Nevery delta
* ID, group-ID are documented in :doc:`fix <fix>` command
* numdiff = style name of this fix command
* Nevery = calculate force by finite difference every this many timesteps
* Delta = finite difference displacement length (distance units)
* delta = finite difference displacement length (distance units)
Examples
""""""""
.. parsed-literal::
.. code-block:: LAMMPS
fix 1 all numdiff 1 0.0001
fix 1 all numdiff 10 1e-6
@ -40,12 +37,12 @@ have their averages computed. Results are set to 0.0 for atoms not in
the group.
This fix performs a loop over all atoms (in the group). For each atom
and each component of force it adds *Delta* to the position, and
and each component of force it adds *delta* to the position, and
computes the new energy of the entire system. It then subtracts
*Delta* from the original position and again computes the new energy
*delta* from the original position and again computes the new energy
of the system. It then restores the original position. That
component of force is calculated as the difference in energy divided
by two times *Delta*.
by two times *delta*.
.. note::
@ -76,18 +73,15 @@ by two times *Delta*.
----------
The *Nevery*\ argument specifies on what timesteps the force will
The *Nevery* argument specifies on what timesteps the force will
be used calculated by finite difference.
The *Delta*\ argument specifies the positional displacement each
The *delta* argument specifies the positional displacement each
atom will undergo.
----------
**Restart, fix\_modify, output, run start/stop, minimize info:**
**Restart, fix_modify, output, run start/stop, minimize info:**
No information about this fix is written to :doc:`binary restart files
<restart>`. None of the :doc:`fix_modify <fix_modify>` options are
@ -97,7 +91,7 @@ This fix produces a per-atom array which can be accessed by various
:doc:`output commands <Howto_output>`, which stores the components of
the force on each atom as calculated by finite difference. The
per-atom values can only be accessed on timesteps that are multiples
of *Nfreq* since that is when the finite difference forces are
of *Nevery* since that is when the finite difference forces are
calculated.
No parameter of this fix can be used with the *start/stop* keywords of