forked from lijiext/lammps
66 lines
1.6 KiB
Plaintext
66 lines
1.6 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,Commands_all.html)
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:line
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improper_style inversion/harmonic command :h3
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[Syntax:]
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improper_style inversion/harmonic :pre
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[Examples:]
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improper_style inversion/harmonic
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improper_coeff 1 18.776340 0.000000 :pre
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[Description:]
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The {inversion/harmonic} improper style follows the Wilson-Decius
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out-of-plane angle definition and uses an harmonic potential:
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:c,image(Eqs/improper_inversion_harmonic.jpg)
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where K is the force constant and omega is the angle evaluated for
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all three axis-plane combinations centered around the atom I. For
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the IL axis and the IJK plane omega looks as follows:
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:c,image(JPG/umbrella.jpg)
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Note that the {inversion/harmonic} angle term evaluation differs to
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the "improper_umbrella"_improper_umbrella.html due to the cyclic
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evaluation of all possible angles omega.
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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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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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:line
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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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USER-MOFFF package. See the "Build package"_Build_package.html doc
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page for more info.
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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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