forked from lijiext/lammps
89 lines
3.0 KiB
Plaintext
89 lines
3.0 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 harmonic command :h3
|
|
improper_style harmonic/omp command :h3
|
|
|
|
[Syntax:]
|
|
|
|
improper_style harmonic :pre
|
|
|
|
[Examples:]
|
|
|
|
improper_style harmonic
|
|
improper_coeff 1 100.0 0 :pre
|
|
|
|
[Description:]
|
|
|
|
The {harmonic} improper style uses the potential
|
|
|
|
:c,image(Eqs/improper_harmonic.jpg)
|
|
|
|
where X is the improper angle, X0 is its equilibrium value, and K is a
|
|
prefactor. Note that the usual 1/2 factor is included in K.
|
|
|
|
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 X
|
|
is the angle between the plane of I,J,K and the plane of J,K,L.
|
|
Alternatively, you can think of atoms J,K,L as being in a plane, and
|
|
atom I above the plane, and X 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/radian^2)
|
|
X0 (degrees) :ul
|
|
|
|
X0 is specified in degrees, but LAMMPS converts it to radians
|
|
internally; hence the units of K are in energy/radian^2.
|
|
|
|
:line
|
|
|
|
Styles with a {cuda}, {gpu}, {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 in "Section_accelerate"_Section_accelerate.html of the
|
|
manual. 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 USER-CUDA, GPU, USER-OMP and OPT
|
|
packages, respectively. They are only enabled if LAMMPS was built with
|
|
those packages. See the "Making LAMMPS"_Section_start.html#start_3
|
|
section 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"_Section_start.html#start_7 when you invoke LAMMPS, or you can
|
|
use the "suffix"_suffix.html command in your input script.
|
|
|
|
See "Section_accelerate"_Section_accelerate.html of the manual 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
|
|
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
|