98 lines
2.8 KiB
ReStructuredText
98 lines
2.8 KiB
ReStructuredText
.. index:: angle_style sdk
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angle_style sdk command
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=======================
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angle_style sdk/omp 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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angle_style sdk
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angle_style sdk/omp
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Examples
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""""""""
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.. code-block:: LAMMPS
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angle_style sdk
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angle_coeff 1 300.0 107.0
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Description
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"""""""""""
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The *sdk* angle style is a combination of the harmonic angle potential,
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.. math::
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E = K (\theta - \theta_0)^2
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where :math:`\theta_0` is the equilibrium value of the angle and :math:`K` a prefactor,
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with the *repulsive* part of the non-bonded *lj/sdk* pair style
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between the atoms 1 and 3. This angle potential is intended for
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coarse grained MD simulations with the CMM parameterization using the
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:doc:`pair\_style lj/sdk <pair_sdk>`. Relative to the pair\_style
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*lj/sdk*\ , however, the energy is shifted by *epsilon*\ , to avoid sudden
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jumps. Note that the usual 1/2 factor is included in :math:`K`.
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The following coefficients must be defined for each angle type via the
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:doc:`angle\_coeff <angle_coeff>` command as in the example above:
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* :math:`K` (energy/radian\^2)
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* :math:`\theta_0` (degrees)
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:math:`\theta_0` is specified in degrees, but LAMMPS converts it to radians
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internally; hence the units of :math:`K` are in energy/radian\^2.
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The also required *lj/sdk* parameters will be extracted automatically
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from the pair\_style.
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----------
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Styles with a *gpu*\ , *intel*\ , *kk*\ , *omp*\ , or *opt* suffix are
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functionally the same as the corresponding style without the suffix.
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They have been optimized to run faster, depending on your available
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hardware, as discussed on the :doc:`Speed packages <Speed_packages>` doc
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page. The accelerated styles take the same arguments and should
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produce the same results, except for round-off and precision issues.
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These accelerated styles are part of the GPU, USER-INTEL, KOKKOS,
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USER-OMP and OPT packages, respectively. They are only enabled if
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LAMMPS was built with those packages. See the :doc:`Build package <Build_package>` doc page for more info.
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You can specify the accelerated styles explicitly in your input script
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by including their suffix, or you can use the :doc:`-suffix command-line switch <Run_options>` when you invoke LAMMPS, or you can use the
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:doc:`suffix <suffix>` command in your input script.
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See the :doc:`Speed packages <Speed_packages>` doc page for more
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instructions on how to use the accelerated styles effectively.
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----------
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Restrictions
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""""""""""""
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This angle style can only be used if LAMMPS was built with the
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USER-CGSDK package. See the :doc:`Build package <Build_package>` doc
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page for more info.
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Related commands
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""""""""""""""""
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:doc:`angle\_coeff <angle_coeff>`, :doc:`angle\_style harmonic <angle_harmonic>`, :doc:`pair\_style lj/sdk <pair_sdk>`,
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:doc:`pair\_style lj/sdk/coul/long <pair_sdk>`
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**Default:** none
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