forked from lijiext/lammps
84 lines
2.8 KiB
Plaintext
84 lines
2.8 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
|
|
|
|
fix qeq/reax command :h3
|
|
|
|
[Syntax:]
|
|
|
|
fix ID group-ID qeq/reax Nevery cutlo cuthi tolerance params :pre
|
|
|
|
ID, group-ID are documented in "fix"_fix.html command
|
|
qeq/reax = style name of this fix command
|
|
Nevery = perform QEq every this many steps
|
|
cutlo,cuthi = lo and hi cutoff for Taper radius
|
|
tolerance = precision to which charges will be equilibrated
|
|
params = reax/c or a filename :ul
|
|
|
|
[Examples:]
|
|
|
|
fix 1 all qeq/reax 1 0.0 10.0 1.0e-6 reax/c
|
|
fix 1 all qeq/reax 1 0.0 10.0 1.0e-6 param.qeq :pre
|
|
|
|
[Description:]
|
|
|
|
Perform the charge equilibration (QEq) method as described in "(Rappe
|
|
and Goddard, 1991)"_#Rappe_1991 and formulated in "(Nakano,
|
|
1997)"_#Nakano_1997. It is typically used in conjunction with the
|
|
ReaxFF force field model as implemented in the "pair_style
|
|
reax/c"_pair_reax_c.html command.
|
|
|
|
The QEq method minimizes the electrostatic energy of the system by
|
|
adjusting the partial charge on individual atoms based on interactions
|
|
with their neighbors. It reqires some parameters for each atom type.
|
|
If the {params} setting above is the word "reax/c", then these are
|
|
extracted from the "pair_style reax/c"_pair_reax_c.html command and
|
|
the ReaxFF force field file it reads in. If a file name is specified
|
|
for {params}, then the parameters are taken from the specified file
|
|
and the file must contain one line for each atom type. Each line
|
|
should be formatted as follows:
|
|
|
|
itype chi eta gamma :pre
|
|
|
|
where {itype} is the atom type from 1 to Ntypes, {chi} denotes the
|
|
electronegativity in energy units, {eta} denotes the self-Coulomb
|
|
potential in energy units, and {gamma} denotes the valence orbital
|
|
exponent. Note that these 3 quantities are also in the ReaxFF
|
|
potential file, except that eta is defined here as twice the eta value
|
|
in the ReaxFF file.
|
|
|
|
[Restart, fix_modify, output, run start/stop, minimize info:]
|
|
|
|
No information about this fix is written to "binary restart
|
|
files"_restart.html. No global scalar or vector or per-atom
|
|
quantities are stored by this fix for access by various "output
|
|
commands"_Section_howto.html#4_15. No parameter of this fix can be
|
|
used with the {start/stop} keywords of the "run"_run.html command.
|
|
|
|
This fix is invoked during "energy minimization"_minimize.html.
|
|
|
|
[Restrictions:]
|
|
|
|
This fix is part of the "user-reaxc" package. It is only enabled if
|
|
LAMMPS was built with that package. See the "Making
|
|
LAMMPS"_Section_start.html#2_3 section for more info.
|
|
|
|
[Related commands:]
|
|
|
|
"pair_style reax/c"_pair_reax_c.html
|
|
|
|
[Default:] none
|
|
|
|
:line
|
|
|
|
:link(Rappe_1991)
|
|
[(Rappe)] Rappe and Goddard III, Journal of Physical Chemistry, 105,
|
|
3358-3363 (1991).
|
|
|
|
:link(Nakano_1997)
|
|
[(Nakano)] Nakano, Computer Physics Communications, 104, 59-69 (1997).
|