71 lines
1.7 KiB
ReStructuredText
71 lines
1.7 KiB
ReStructuredText
.. index:: bond_style harmonic/shift/cut
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.. index:: bond_style harmonic/shift/cut/omp
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bond_style harmonic/shift/cut command
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=====================================
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Accelerator Variants: *harmonic/shift/cut/omp*
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Syntax
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""""""
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.. code-block:: LAMMPS
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bond_style harmonic/shift/cut
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Examples
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""""""""
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.. code-block:: LAMMPS
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bond_style harmonic/shift/cut
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bond_coeff 5 10.0 0.5 1.0
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Description
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"""""""""""
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The *harmonic/shift/cut* bond style is a shifted harmonic bond that
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uses the potential
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.. math::
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E = \frac{U_{\text{min}}}{(r_0-r_c)^2} \left[ (r-r_0)^2-(r_c-r_0)^2 \right]
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where :math:`r_0` is the equilibrium bond distance, and rc the critical distance.
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The bond potential is zero for distances :math:`r > r_c`. The potential is :math:`-U_{\text{min}}`
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at :math:`r_0` and zero at :math:`r_c`. The spring constant is :math:`k = U_{\text{min}} / [ 2 (r_0-r_c)^2]`.
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The following coefficients must be defined for each bond type via the
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:doc:`bond_coeff <bond_coeff>` command as in the example above, or in
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the data file or restart files read by the :doc:`read_data <read_data>`
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or :doc:`read_restart <read_restart>` commands:
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* :math:`U_{\text{min}}` (energy)
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* :math:`r_0` (distance)
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* :math:`r_c` (distance)
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----------
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.. include:: accel_styles.rst
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----------
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Restrictions
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""""""""""""
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This bond style can only be used if LAMMPS was built with the
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EXTRA-MOLECULE 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:`bond_coeff <bond_coeff>`, :doc:`delete_bonds <delete_bonds>`,
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:doc:`bond_harmonic <bond_harmonic>`,
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:doc:`bond_style harmonic/shift <bond_harmonic_shift>`
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Default
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"""""""
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none
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