91 lines
2.8 KiB
ReStructuredText
91 lines
2.8 KiB
ReStructuredText
.. index:: compute dipole
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.. index:: compute dipole/tip4p
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compute dipole command
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======================
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compute dipole/tip4p command
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============================
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Syntax
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""""""
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.. code-block:: LAMMPS
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compute ID group-ID style arg
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* ID, group-ID are documented in :doc:`compute <compute>` command
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* style = *dipole* or *dipole/tip4p*
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* arg = *mass* or *geometry* = use COM or geometric center for charged chunk correction (optional)
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Examples
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""""""""
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.. code-block:: LAMMPS
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compute 1 fluid dipole
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compute dw water dipole geometry
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compute dw water dipole/tip4p
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Description
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"""""""""""
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Define a computation that calculates the dipole vector and total dipole
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for a group of atoms.
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These computes calculate the x,y,z coordinates of the dipole vector and
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the total dipole moment for the atoms in the compute group. This
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includes all effects due to atoms passing through periodic boundaries.
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For a group with a net charge the resulting dipole is made position
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independent by subtracting the position vector of the center of mass or
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geometric center times the net charge from the computed dipole
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vector. Both per-atom charges and per-atom dipole moments, if present,
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contribute to the computed dipole.
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.. versionadded:: 28Mar2023
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Compute *dipole/tip4p* includes adjustments for the charge carrying
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point M in molecules with TIP4P water geometry. The corresponding
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parameters are extracted from the pair style.
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.. note::
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The coordinates of an atom contribute to the dipole in "unwrapped"
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form, by using the image flags associated with each atom. See the
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:doc:`dump custom <dump>` command for a discussion of "unwrapped"
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coordinates. See the Atoms section of the :doc:`read_data
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<read_data>` command for a discussion of image flags and how they are
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set for each atom. You can reset the image flags (e.g., to 0) before
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invoking this compute by using the :doc:`set image <set>` command.
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Output info
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"""""""""""
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These computes calculate a global scalar containing the magnitude of the
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computed dipole moment and a global vector of length 3 with the dipole
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vector. See the :doc:`Howto output <Howto_output>` page for an overview
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of LAMMPS output options.
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The computed values are "intensive". The array values will be in
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dipole units (i.e., charge :doc:`units <units>` times distance
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:doc:`units <units>`).
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Restrictions
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""""""""""""
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Compute style *dipole/tip4p* is part of the EXTRA-COMPUTE package. It is
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only enabled if LAMMPS was built with that package. See the :doc:`Build
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package <Build_package>` page for more info.
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Compute style *dipole/tip4p* can only be used with tip4p pair styles.
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Related commands
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""""""""""""""""
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:doc:`compute dipole/chunk <compute_dipole_chunk>`
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Default
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"""""""
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Using the center of mass is the default setting for the net charge correction.
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