Update docs: angle_cross

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$$

  E = K_{SS} \left(r_{12}-r_{12,0}\right)\left(r_{32}-r_{32,0}\right) + K_{BS0}\left(r_{12}-r_{12,0}\right)\left(\theta-\theta_0\right) + K_{BS1}\left(r_{32}-r_{32,0}\right)\left(\theta-\theta_0\right)

$$

\end{document}

.. index:: angle\_style cross

.. index:: angle_style cross

angle\_style cross command

angle_style cross command

==========================

Syntax

""""""

.. parsed-literal::

.. code-block:: LAMMPS

   angle_style cross

""""""""

.. parsed-literal::

.. code-block:: LAMMPS

   angle_style cross

   angle_coeff 1 200.0 100.0 100.0 1.25 1.25 107.0

The *cross* angle style uses a potential that couples the bond stretches of

a bend with the angle stretch of that bend:

.. image:: Eqs/angle_cross.jpg

   :align: center

.. math::

where r12,0 is the rest value of the bond length between atom 1 and 2,

r32,0 is the rest value of the bond length between atom 2 and 2,

and theta0 is the rest value of the angle. KSS is the force constant of

the bond stretch-bond stretch term and KBS0 and KBS1 are the force constants

   E = K_{SS} \left(r_{12}-r_{12,0}\right)\left(r_{32}-r_{32,0}\right) + K_{BS0}\left(r_{12}-r_{12,0}\right)\left(\theta-\theta_0\right) + K_{BS1}\left(r_{32}-r_{32,0}\right)\left(\theta-\theta_0\right)

where :math:`r_{12,0}` is the rest value of the bond length between atom 1 and 2,

:math:`r_{32,0}` is the rest value of the bond length between atom 3 and 2,

and :math:`\theta_0` is the rest value of the angle. :math:`K_{SS}` is the force constant of

the bond stretch-bond stretch term and :math:`K_{BS0}` and :math:`K_{BS1}` are the force constants

of the bond stretch-angle stretch terms.

The following coefficients must be defined for each angle type via the

the data file or restart files read by the :doc:`read\_data <read_data>`

or :doc:`read\_restart <read_restart>` commands:

* KSS (energy/distance\^2)

* KBS0 (energy/distance/rad)

* KBS1 (energy/distance/rad)

* r12,0 (distance)

* r32,0 (distance)

* theta0 (degrees)

* :math:`K_{SS}` (energy/distance\^2)

* :math:`K_{BS0}` (energy/distance/rad)

* :math:`K_{BS1}` (energy/distance/rad)

* :math:`r_{12,0}` (distance)

* :math:`r_{32,0}` (distance)

* :math:`\theta_0` (degrees)

Theta0 is specified in degrees, but LAMMPS converts it to radians

internally; hence the units of KBS0 and KBS1 are in energy/distance/radian.

:math:`\theta_0` is specified in degrees, but LAMMPS converts it to radians

internally; hence the units of :math:`K_{BS0}` and :math:`K_{BS1}` are in energy/distance/radian.

Restrictions

""""""""""""

:doc:`angle\_coeff <angle_coeff>`

**Default:** none

----------

.. _lws: http://lammps.sandia.gov

.. _ld: Manual.html

.. _lc: Commands_all.html

"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c

:link(lws,http://lammps.sandia.gov)

:link(ld,Manual.html)

:link(lc,Commands_all.html)

:line

angle_style cross command :h3

[Syntax:]

angle_style cross :pre

[Examples:]

angle_style cross

angle_coeff 1 200.0 100.0 100.0 1.25 1.25 107.0 :pre

[Description:]

The {cross} angle style uses a potential that couples the bond stretches of

a bend with the angle stretch of that bend:

:c,image(Eqs/angle_cross.jpg)

where r12,0 is the rest value of the bond length between atom 1 and 2,

r32,0 is the rest value of the bond length between atom 2 and 2,

and theta0 is the rest value of the angle. KSS is the force constant of

the bond stretch-bond stretch term and KBS0 and KBS1 are the force constants

of the bond stretch-angle stretch terms.

The following coefficients must be defined for each angle type via the

"angle_coeff"_angle_coeff.html command as in the example above, or in

the data file or restart files read by the "read_data"_read_data.html

or "read_restart"_read_restart.html commands:

KSS (energy/distance^2)

KBS0 (energy/distance/rad)

KBS1 (energy/distance/rad)

r12,0 (distance)

r32,0 (distance)

theta0 (degrees) :ul

Theta0 is specified in degrees, but LAMMPS converts it to radians

internally; hence the units of KBS0 and KBS1 are in energy/distance/radian.

[Restrictions:]

This angle style can only be used if LAMMPS was built with the

USER_YAFF package.  See the "Build package"_Build_package.html doc

page for more info.

[Related commands:]

"angle_coeff"_angle_coeff.html

[Default:] none

:line