2010-10-26 04:29:32 +08:00
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"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c
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:link(lws,http://lammps.sandia.gov)
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:link(ld,Manual.html)
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:link(lc,Section_commands.html#comm)
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:line
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improper_style umbrella command :h3
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2011-12-01 23:35:32 +08:00
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improper_style umbrella/omp command :h3
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2010-10-26 04:29:32 +08:00
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[Syntax:]
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improper_style umbrella :pre
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[Examples:]
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improper_style umbrella
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improper_coeff 1 100.0 180.0 :pre
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[Description:]
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The {umbrella} improper style uses the following potential, which is
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commonly referred to as a classic inversion and used in the
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2011-08-26 01:01:01 +08:00
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"DREIDING"_Section_howto.html#howto_4 force field:
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2010-10-26 04:29:32 +08:00
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:c,image(Eqs/improper_umbrella.jpg)
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where K is the force constant and omega is the angle between the IL
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axis and the IJK plane:
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:c,image(Eqs/umbrella.jpg)
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If omega0 = 0 the potential term has a minimum for the planar
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structure. Otherwise it has two minima at +/- omega0, with a barrier
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in between.
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See "(Mayo)"_#Mayo for a description of the DREIDING force field.
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The following coefficients must be defined for each improper type via
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the "improper_coeff"_improper_coeff.html command as in the example
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above, or in the data file or restart files read by the
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"read_data"_read_data.html or "read_restart"_read_restart.html
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commands:
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K (energy)
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omega0 (degrees) :ul
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2011-12-01 23:35:32 +08:00
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:line
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2014-08-15 00:30:25 +08:00
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Styles with a {cuda}, {gpu}, {intel}, {kk}, {omp}, or {opt} suffix are
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functionally the same as the corresponding style without the suffix.
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They have been optimized to run faster, depending on your available
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hardware, as discussed in "Section_accelerate"_Section_accelerate.html
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of the manual. The accelerated styles take the same arguments and
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should produce the same results, except for round-off and precision
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issues.
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These accelerated styles are part of the USER-CUDA, GPU, USER-INTEL,
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KOKKOS, USER-OMP and OPT packages, respectively. They are only
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enabled if LAMMPS was built with those packages. See the "Making
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LAMMPS"_Section_start.html#start_3 section for more info.
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2011-12-01 23:35:32 +08:00
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You can specify the accelerated styles explicitly in your input script
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by including their suffix, or you can use the "-suffix command-line
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2012-01-28 07:39:14 +08:00
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switch"_Section_start.html#start_7 when you invoke LAMMPS, or you can
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2011-12-01 23:35:32 +08:00
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use the "suffix"_suffix.html command in your input script.
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2011-12-14 04:35:35 +08:00
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See "Section_accelerate"_Section_accelerate.html of the manual for
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more instructions on how to use the accelerated styles effectively.
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2011-12-01 23:35:32 +08:00
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:line
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2010-10-26 04:29:32 +08:00
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[Restrictions:]
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This improper style can only be used if LAMMPS was built with the
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2015-02-26 05:42:32 +08:00
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MOLECULE package (which it is by default). See the "Making
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2011-08-26 00:46:23 +08:00
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LAMMPS"_Section_start.html#start_3 section for more info on packages.
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2010-10-26 04:29:32 +08:00
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[Related commands:]
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"improper_coeff"_improper_coeff.html
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[Default:] none
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:line
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:link(Mayo)
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[(Mayo)] Mayo, Olfason, Goddard III, J Phys Chem, 94, 8897-8909
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(1990),
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