77 lines
1.8 KiB
ReStructuredText
77 lines
1.8 KiB
ReStructuredText
.. index:: bond_style harmonic/shift
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.. index:: bond_style harmonic/shift/omp
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bond_style harmonic/shift command
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=================================
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Accelerator Variants: *harmonic/shift/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
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Examples
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""""""""
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.. code-block:: LAMMPS
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bond_style harmonic/shift
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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* bond style is a shifted harmonic bond that uses
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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 :math:`r_c` the
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critical distance. The potential energy has the value
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:math:`-U_{\text{min}}` at :math:`r_0` and zero at :math:`r_c`. This
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bond style differs from :doc:`bond_style harmonic <bond_harmonic>`
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by the value of the potential energy.
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The equivalent spring constant value *K* for use with :doc:`bond_style
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harmonic <bond_harmonic>` can be computed using :math:`K =
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U_{\text{min}} / [(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 style harmonic <bond_harmonic>`,
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:doc:`bond style harmonic/shift/cut <bond_harmonic_shift_cut>`
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Default
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"""""""
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none
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