124 lines
5.1 KiB
ReStructuredText
124 lines
5.1 KiB
ReStructuredText
.. index:: angle_style
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angle_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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angle_style style
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* style = *none* or *zero* or *hybrid* or *amoeba* or *charmm* or *class2* or *class2/p6* or *cosine* or *cosine/buck6d* or *cosine/delta* or *cosine/periodic* or *cosine/shift* or *cosine/shift/exp* or *cosine/squared* or *cosine/squared/restricted* or *cross* or *dipole* or *fourier* or *fourier/simple* or *gaussian* or *harmonic* or *lepton* or *mm3* or *quartic* or *spica* or *table*
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Examples
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""""""""
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.. code-block:: LAMMPS
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angle_style harmonic
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angle_style charmm
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angle_style hybrid harmonic cosine
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Description
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"""""""""""
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Set the formula(s) LAMMPS uses to compute angle interactions between
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triplets of atoms, which remain in force for the duration of the
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simulation. The list of angle triplets 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.
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Hybrid models where angles are computed using different angle
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potentials can be setup using the *hybrid* angle style.
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The coefficients associated with a angle style can be specified in a
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data or restart file or via the :doc:`angle_coeff <angle_coeff>` command.
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All angle potentials store their coefficient data in binary restart
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files which means angle_style and :doc:`angle_coeff <angle_coeff>`
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commands do not need to be re-specified in an input script that
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restarts a simulation. See the :doc:`read_restart <read_restart>`
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command for details on how to do this. The one exception is that
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angle_style *hybrid* only stores the list of sub-styles in the restart
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file; angle coefficients need to be re-specified.
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.. note::
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When both an angle 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 3 bonded atoms.
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In the formulas listed for each angle style, *theta* is the angle
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between the 3 atoms in the angle.
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----------
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Here is an alphabetic list of angle styles defined in LAMMPS. Click on
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the style to display the formula it computes and coefficients
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specified by the associated :doc:`angle_coeff <angle_coeff>` 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 angle_style command, and coefficients
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specified by the associated :doc:`angle_coeff <angle_coeff>` 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 angle <angle>` page are followed by one or more
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of (g,i,k,o,t) to indicate which accelerated styles exist.
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* :doc:`none <angle_none>` - turn off angle interactions
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* :doc:`zero <angle_zero>` - topology but no interactions
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* :doc:`hybrid <angle_hybrid>` - define multiple styles of angle interactions
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* :doc:`amoeba <angle_amoeba>` - AMOEBA angle
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* :doc:`charmm <angle_charmm>` - CHARMM angle
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* :doc:`class2 <angle_class2>` - COMPASS (class 2) angle
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* :doc:`class2/p6 <angle_class2>` - COMPASS (class 2) angle expanded to 6th order
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* :doc:`cosine <angle_cosine>` - angle with cosine term
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* :doc:`cosine/buck6d <angle_cosine_buck6d>` - same as cosine with Buckingham term between 1-3 atoms
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* :doc:`cosine/delta <angle_cosine_delta>` - angle with difference of cosines
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* :doc:`cosine/periodic <angle_cosine_periodic>` - DREIDING angle
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* :doc:`cosine/shift <angle_cosine_shift>` - angle cosine with a shift
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* :doc:`cosine/shift/exp <angle_cosine_shift_exp>` - cosine with shift and exponential term in spring constant
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* :doc:`cosine/squared <angle_cosine_squared>` - angle with cosine squared term
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* :doc:`cosine/squared/restricted <angle_cosine_squared_restricted>` - angle with restricted cosine squared term
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* :doc:`cross <angle_cross>` - cross term coupling angle and bond lengths
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* :doc:`dipole <angle_dipole>` - angle that controls orientation of a point dipole
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* :doc:`fourier <angle_fourier>` - angle with multiple cosine terms
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* :doc:`fourier/simple <angle_fourier_simple>` - angle with a single cosine term
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* :doc:`gaussian <angle_gaussian>` - multi-centered Gaussian-based angle potential
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* :doc:`harmonic <angle_harmonic>` - harmonic angle
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* :doc:`lepton <angle_lepton>` - angle potential from evaluating a string
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* :doc:`mesocnt <angle_mesocnt>` - piecewise harmonic and linear angle for bending-buckling of nanotubes
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* :doc:`mm3 <angle_mm3>` - anharmonic angle
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* :doc:`quartic <angle_quartic>` - angle with cubic and quartic terms
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* :doc:`spica <angle_spica>` - harmonic angle with repulsive SPICA pair style between 1-3 atoms
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* :doc:`table <angle_table>` - tabulated by angle
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----------
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Restrictions
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""""""""""""
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Angle styles can only be set for atom_styles that allow angles to be
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defined.
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Most angle 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 bond potentials tell if it is part of a package.
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Related commands
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""""""""""""""""
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:doc:`angle_coeff <angle_coeff>`
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Default
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"""""""
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.. code-block:: LAMMPS
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angle_style none
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