117 lines
4.2 KiB
ReStructuredText
117 lines
4.2 KiB
ReStructuredText
.. index:: improper_style
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improper_style 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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improper_style style
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* style = *none* or *hybrid* or *class2* or *cvff* or *harmonic*
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Examples
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""""""""
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.. code-block:: LAMMPS
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improper_style harmonic
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improper_style cvff
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improper_style hybrid cvff harmonic
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Description
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"""""""""""
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Set the formula(s) LAMMPS uses to compute improper interactions
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between quadruplets of atoms, which remain in force for the duration
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of the simulation. The list of improper quadruplets is read in by a
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:doc:`read_data <read_data>` or :doc:`read_restart <read_restart>` command
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from a data or restart file. Note that the ordering of the 4 atoms in
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an improper quadruplet determines the definition of the improper
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angle used in the formula for each style. See the doc pages of
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individual styles for details.
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Hybrid models where impropers are computed using different improper
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potentials can be setup using the *hybrid* improper style.
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The coefficients associated with an improper style can be specified in
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a data or restart file or via the :doc:`improper_coeff <improper_coeff>`
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command.
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All improper potentials store their coefficient data in binary restart
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files which means improper_style and
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:doc:`improper_coeff <improper_coeff>` commands do not need to be
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re-specified in an input script that restarts a simulation. See the
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:doc:`read_restart <read_restart>` command for details on how to do
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this. The one exception is that improper_style *hybrid* only stores
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the list of sub-styles in the restart file; improper coefficients need
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to be re-specified.
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.. note::
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When both an improper and pair style is defined, the
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:doc:`special_bonds <special_bonds>` command often needs to be used to
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turn off (or weight) the pairwise interaction that would otherwise
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exist between a group of 4 bonded atoms.
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----------
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Here is an alphabetic list of improper styles defined in LAMMPS.
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Click on the style to display the formula it computes and coefficients
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specified by the associated :doc:`improper_coeff <improper_coeff>`
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command.
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Click on the style to display the formula it computes, any additional
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arguments specified in the improper_style command, and coefficients
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specified by the associated :doc:`improper_coeff <improper_coeff>`
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command.
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There are also additional accelerated pair styles included in the
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LAMMPS distribution for faster performance on CPUs, GPUs, and KNLs.
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The individual style names on the :ref:`Commands improper <improper>` page are followed by one or
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more of (g,i,k,o,t) to indicate which accelerated styles exist.
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* :doc:`none <improper_none>` - turn off improper interactions
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* :doc:`zero <improper_zero>` - topology but no interactions
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* :doc:`hybrid <improper_hybrid>` - define multiple styles of improper interactions
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* :doc:`amoeba <improper_amoeba>` - AMOEBA out-of-plane improper
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* :doc:`class2 <improper_class2>` - COMPASS (class 2) improper
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* :doc:`cossq <improper_cossq>` - improper with a cosine squared term
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* :doc:`cvff <improper_cvff>` - CVFF improper
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* :doc:`distance <improper_distance>` - improper based on distance between atom planes
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* :doc:`distharm <improper_distharm>` - improper that is harmonic in the out-of-plane distance
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* :doc:`fourier <improper_fourier>` - improper with multiple cosine terms
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* :doc:`harmonic <improper_harmonic>` - harmonic improper
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* :doc:`inversion/harmonic <improper_inversion_harmonic>` - harmonic improper with Wilson-Decius out-of-plane definition
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* :doc:`ring <improper_ring>` - improper which prevents planar conformations
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* :doc:`umbrella <improper_umbrella>` - DREIDING improper
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:doc:`sqdistharm <improper_sqdistharm>` - improper that is harmonic in the square of the out-of-plane distance
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----------
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Restrictions
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""""""""""""
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Improper styles can only be set for atom_style choices that allow
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impropers to be defined.
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Most improper styles are part of the MOLECULE package. They are only
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enabled if LAMMPS was built with that package. See the :doc:`Build package <Build_package>` page for more info. The doc pages for
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individual improper potentials tell if it is part of a package.
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Related commands
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""""""""""""""""
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:doc:`improper_coeff <improper_coeff>`
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Default
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"""""""
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.. code-block:: LAMMPS
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improper_style none
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