forked from lijiext/lammps
80 lines
2.8 KiB
Plaintext
80 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
|
|
|
|
pair_write command :h3
|
|
|
|
[Syntax:]
|
|
|
|
pair_write itype jtype N style inner outer file keyword Qi Qj :pre
|
|
|
|
itype,jtype = 2 atom types
|
|
N = # of values
|
|
style = {r} or {rsq} or {bitmap}
|
|
inner,outer = inner and outer cutoff (distance units)
|
|
file = name of file to write values to
|
|
keyword = section name in file for this set of tabulated values
|
|
Qi,Qj = 2 atom charges (charge units) (optional) :ul
|
|
|
|
[Examples:]
|
|
|
|
pair_write 1 3 500 r 1.0 10.0 table.txt LJ
|
|
pair_write 1 1 1000 rsq 2.0 8.0 table.txt Yukawa_1_1 -0.5 0.5 :pre
|
|
|
|
[Description:]
|
|
|
|
Write energy and force values to a file as a function of distance for
|
|
the currently defined pair potential. This is useful for plotting the
|
|
potential function or otherwise debugging its values. If the file
|
|
already exists, the table of values is appended to the end of the file
|
|
to allow multiple tables of energy and force to be included in one
|
|
file.
|
|
|
|
The energy and force values are computed at distances from inner to
|
|
outer for 2 interacting atoms of type itype and jtype, using the
|
|
appropriate "pair_coeff"_pair_coeff.html coefficients. If the style
|
|
is {r}, then N distances are used, evenly spaced in r; if the style is
|
|
{rsq}, N distances are used, evenly spaced in r^2.
|
|
|
|
For example, for N = 7, style = {r}, inner = 1.0, and outer = 4.0,
|
|
values are computed at r = 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0.
|
|
|
|
If the style is {bitmap}, then 2^N values are written to the file in a
|
|
format and order consistent with how they are read in by the
|
|
"pair_coeff"_pair_coeff.html command for pair style {table}. For
|
|
reasonable accuracy in a bitmapped table, choose N >= 12, an {inner}
|
|
value that is smaller than the distance of closest approach of 2
|
|
atoms, and an {outer} value <= cutoff of the potential.
|
|
|
|
If the pair potential is computed between charged atoms, the charges
|
|
of the pair of interacting atoms can optionally be specified. If not
|
|
specified, values of Qi = Qj = 1.0 are used.
|
|
|
|
The file is written in the format used as input for the
|
|
"pair_style"_pair_style.html {table} option with {keyword} as the
|
|
section name. Each line written to the file lists an index number
|
|
(1-N), a distance (in distance units), an energy (in energy units),
|
|
and a force (in force units).
|
|
|
|
[Restrictions:]
|
|
|
|
All force field coefficients for pair and other kinds of interactions
|
|
must be set before this command can be invoked.
|
|
|
|
Due to how the pairwise force is computed, an inner value > 0.0 must
|
|
be specified even if the potential has a finite value at r = 0.0.
|
|
|
|
For EAM potentials, the pair_write command only tabulates the
|
|
pairwise portion of the potential, not the embedding portion.
|
|
|
|
[Related commands:]
|
|
|
|
"pair_style table"_pair_table.html,
|
|
"pair_style"_pair_style.html, "pair_coeff"_pair_coeff.html
|
|
|
|
[Default:] none
|