"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

improper_style umbrella command :h3
improper_style umbrella/omp command :h3

[Syntax:]

improper_style umbrella :pre

[Examples:]

improper_style umbrella
improper_coeff 1 100.0 180.0 :pre

[Description:]

The {umbrella} improper style uses the following potential, which is
commonly referred to as a classic inversion and used in the
"DREIDING"_Howto_bioFF.html force field:

:c,image(Eqs/improper_umbrella.jpg)

where K is the force constant and omega is the angle between the IL
axis and the IJK plane:

:c,image(JPG/umbrella.jpg)

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 "(Mayo)"_#umbrella-Mayo for a description of the DREIDING force field.

The following coefficients must be defined for each improper type via
the "improper_coeff"_improper_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:

K (energy)
omega0 (degrees) :ul

:line

Styles with a {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 on the "Speed packages"_Speed_packages.html doc
page.  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 GPU, USER-INTEL, KOKKOS,
USER-OMP and OPT packages, respectively.  They are only enabled if
LAMMPS was built with those packages.  See the "Build
package"_Build_package.html doc page for more info.

You can specify the accelerated styles explicitly in your input script
by including their suffix, or you can use the "-suffix command-line
switch"_Run_options.html when you invoke LAMMPS, or you can use the
"suffix"_suffix.html command in your input script.

See the "Speed packages"_Speed_packages.html doc page for more
instructions on how to use the accelerated styles effectively.

:line

[Restrictions:]

This improper style can only be used if LAMMPS was built with the
MOLECULE package.  See the "Build package"_Build_package.html doc page
for more info.

[Related commands:]

"improper_coeff"_improper_coeff.html

[Default:] none

:line

:link(umbrella-Mayo)
[(Mayo)] Mayo, Olfason, Goddard III, J Phys Chem, 94, 8897-8909
(1990),
