.. index:: improper_style umbrella improper_style umbrella command =============================== improper_style umbrella/omp command =================================== Syntax """""" .. parsed-literal:: improper_style umbrella Examples """""""" .. parsed-literal:: improper_style umbrella improper_coeff 1 100.0 180.0 Description """"""""""" The *umbrella* improper style uses the following potential, which is commonly referred to as a classic inversion and used in the :ref:`DREIDING ` force field: .. image:: Eqs/improper_umbrella.jpg :align: center where K is the force constant and omega is the angle between the IL axis and the IJK plane: .. image:: Eqs/umbrella.jpg :align: center If omega0 = 0 the potential term has a minimum for the planar structure. Otherwise it has two minima at +/- omega0, with a barrier in between. See :ref:`(Mayo) ` for a description of the DREIDING force field. The following coefficients must be defined for each improper type via the :doc:`improper_coeff ` command as in the example above, or in the data file or restart files read by the :doc:`read_data ` or :doc:`read_restart ` commands: * K (energy) * omega0 (degrees) ---------- Styles with a *cuda*\ , *gpu*\ , *intel*\ , *kk*\ , *omp*\ , or *opt* suffix are functionally the same as the corresponding style without the suffix. They have been optimized to run faster, depending on your available hardware, as discussed in :doc:`Section_accelerate ` of the manual. The accelerated styles take the same arguments and should produce the same results, except for round-off and precision issues. These accelerated styles are part of the USER-CUDA, GPU, USER-INTEL, KOKKOS, USER-OMP and OPT packages, respectively. They are only enabled if LAMMPS was built with those packages. See the :ref:`Making LAMMPS ` section for more info. You can specify the accelerated styles explicitly in your input script by including their suffix, or you can use the :ref:`-suffix command-line switch ` when you invoke LAMMPS, or you can use the :doc:`suffix ` command in your input script. See :doc:`Section_accelerate ` of the manual for more instructions on how to use the accelerated styles effectively. ---------- Restrictions """""""""""" This improper style can only be used if LAMMPS was built with the MOLECULE package (which it is by default). See the :ref:`Making LAMMPS ` section for more info on packages. Related commands """""""""""""""" :doc:`improper_coeff ` **Default:** none ---------- .. _umbrella-Mayo: **(Mayo)** Mayo, Olfason, Goddard III, J Phys Chem, 94, 8897-8909 (1990), .. _lws: http://lammps.sandia.gov .. _ld: Manual.html .. _lc: Section_commands.html#comm