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angle_charmm.txt
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.. index:: angle_style charmm
angle_style charmm command
==========================
angle_style charmm/intel command
================================
angle_style charmm/kk command
=============================
angle_style charmm/omp command
==============================
Syntax
""""""
.. parsed-literal::
angle_style charmm
Examples
""""""""
.. parsed-literal::
angle_style charmm
angle_coeff 1 300.0 107.0 50.0 3.0
Description
"""""""""""
The *charmm* angle style uses the potential
.. image:: Eqs/angle_charmm.jpg
:align: center
with an additional Urey_Bradley term based on the distance *r* between
the 1st and 3rd atoms in the angle. K, theta0, Kub, and Rub are
coefficients defined for each angle type.
See :ref:`(MacKerell) <angle-MacKerell>` for a description of the CHARMM force
field.
The following coefficients must be defined for each angle type via the
:doc:`angle_coeff <angle_coeff>` command as in the example above, or in
the data file or restart files read by the :doc:`read_data <read_data>`
or :doc:`read_restart <read_restart>` commands:
* K (energy/radian^2)
* theta0 (degrees)
* K_ub (energy/distance^2)
* r_ub (distance)
Theta0 is specified in degrees, but LAMMPS converts it to radians
internally; hence the units of K are in energy/radian^2.
----------
Styles with a *gpu*\ , *intel*\ , *kk*\ , *omp*\ , or *opt* suffix are
functionally the same as the corresponding style without the suffix.
They have been optimized to run faster, depending on your available
hardware, as discussed in :doc:`Section_accelerate <Section_accelerate>`
of the manual. The accelerated styles take the same arguments and
should produce the same results, except for round-off and precision
issues.
These accelerated styles are part of the GPU, USER-INTEL, KOKKOS,
USER-OMP and OPT packages, respectively. They are only enabled if
LAMMPS was built with those packages. See the :ref:`Making LAMMPS <start_3>` section for more info.
You can specify the accelerated styles explicitly in your input script
by including their suffix, or you can use the :ref:`-suffix command-line switch <start_7>` when you invoke LAMMPS, or you can
use the :doc:`suffix <suffix>` command in your input script.
See :doc:`Section_accelerate <Section_accelerate>` of the manual for
more instructions on how to use the accelerated styles effectively.
----------
Restrictions
""""""""""""
This angle style can only be used if LAMMPS was built with the
MOLECULE package (which it is by default). See the :ref:`Making LAMMPS <start_3>` section for more info on packages.
Related commands
""""""""""""""""
:doc:`angle_coeff <angle_coeff>`
**Default:** none
----------
.. _angle-MacKerell:
**(MacKerell)** MacKerell, Bashford, Bellott, Dunbrack, Evanseck, Field,
Fischer, Gao, Guo, Ha, et al, J Phys Chem, 102, 3586 (1998).
.. _lws: http://lammps.sandia.gov
.. _ld: Manual.html
.. _lc: Section_commands.html#comm
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