forked from lijiext/lammps
64 lines
1.8 KiB
Plaintext
64 lines
1.8 KiB
Plaintext
"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c
|
|
|
|
:link(lws,http://lammps.sandia.gov)
|
|
:link(ld,Manual.html)
|
|
:link(lc,Section_commands.html#comm)
|
|
|
|
:line
|
|
|
|
improper_style cvff command :h3
|
|
|
|
[Syntax:]
|
|
|
|
improper_style cvff :pre
|
|
|
|
[Examples:]
|
|
|
|
improper_style cvff
|
|
improper_coeff 1 80.0 -1 4 :pre
|
|
|
|
[Description:]
|
|
|
|
The {cvff} improper style uses the potential
|
|
|
|
:c,image(Eqs/improper_cvff.jpg)
|
|
|
|
where phi is the Wilson out-of-plane angle.
|
|
|
|
If the 4 atoms in an improper quadruplet (listed in the data file read
|
|
by the "read_data"_read_data.html command) are ordered I,J,K,L then
|
|
the Wilson angle is between the plane of I,J,K and the plane of J,K,L.
|
|
This is essentially a dihedral angle, which is why the formula for
|
|
this improper style is the same as for "dihedral_style
|
|
harmonic"_dihedral_harmonic.html. Alternatively, you can think of
|
|
atoms J,K,L as being in a plane, and atom I above the plane, and the
|
|
Wilson angle as a measure of how far out-of-plane I is with respect to
|
|
the other 3 atoms.
|
|
|
|
Note that defining 4 atoms to interact in this way, does not mean that
|
|
bonds necessarily exist between I-J, J-K, or K-L, as they would in a
|
|
linear dihedral. Normally, the bonds I-J, I-K, I-L would exist for an
|
|
improper to be defined between the 4 atoms.
|
|
|
|
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)
|
|
d (+1 or -1)
|
|
n (0,1,2,3,4,6) :ul
|
|
|
|
[Restrictions:]
|
|
|
|
This improper style can only be used if LAMMPS was built with the
|
|
"molecular" package (which it is by default). See the "Making
|
|
LAMMPS"_Section_start.html#start_3 section for more info on packages.
|
|
|
|
[Related commands:]
|
|
|
|
"improper_coeff"_improper_coeff.html
|
|
|
|
[Default:] none
|