forked from lijiext/lammps
65 lines
1.5 KiB
Plaintext
65 lines
1.5 KiB
Plaintext
"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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[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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"DREIDING"_Section_howto.html#4_4 force field:
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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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[Restrictions:]
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This improper style can only be used if LAMMPS was built with the
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"molecular" package (which it is by default). See the "Making
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LAMMPS"_Section_start.html#2_3 section for more info on packages.
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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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