forked from lijiext/lammps
98 lines
3.0 KiB
Plaintext
98 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,Commands_all.html)
|
|
|
|
:line
|
|
|
|
fix mvv/dpd command :h3
|
|
fix mvv/edpd command :h3
|
|
fix mvv/tdpd command :h3
|
|
|
|
[Syntax:]
|
|
|
|
fix ID group-ID mvv/dpd lambda :pre
|
|
fix ID group-ID mvv/edpd lambda :pre
|
|
fix ID group-ID mvv/tdpd lambda :pre
|
|
|
|
ID, group-ID are documented in "fix"_fix.html command
|
|
mvv/dpd, mvv/edpd, mvv/tdpd = style name of this fix command
|
|
lambda = (optional) relaxation parameter (unitless) :ul
|
|
|
|
[Examples:]
|
|
|
|
fix 1 all mvv/dpd
|
|
fix 1 all mvv/dpd 0.5
|
|
fix 1 all mvv/edpd
|
|
fix 1 all mvv/edpd 0.5
|
|
fix 1 all mvv/tdpd
|
|
fix 1 all mvv/tdpd 0.5 :pre
|
|
|
|
[Description:]
|
|
|
|
Perform time integration using the modified velocity-Verlet (MVV)
|
|
algorithm to update position and velocity (fix mvv/dpd), or position,
|
|
velocity and temperature (fix mvv/edpd), or position, velocity and
|
|
concentration (fix mvv/tdpd) for particles in the group each timestep.
|
|
|
|
The modified velocity-Verlet (MVV) algorithm aims to improve the
|
|
stability of the time integrator by using an extrapolated version of
|
|
the velocity for the force evaluation:
|
|
|
|
:c,image(Eqs/fix_mvv_dpd.jpg)
|
|
|
|
where the parameter <font size="4">λ</font> depends on the
|
|
specific choice of DPD parameters, and needs to be tuned on a
|
|
case-by-case basis. Specification of a {lambda} value is optional.
|
|
If specified, the setting must be from 0.0 to 1.0. If not specified,
|
|
a default value of 0.5 is used, which effectively reproduces the
|
|
standard velocity-Verlet (VV) scheme. For more details, see
|
|
"Groot"_#Groot2.
|
|
|
|
Fix {mvv/dpd} updates the position and velocity of each atom. It can
|
|
be used with the "pair_style mdpd"_pair_meso.html command or other
|
|
pair styles such as "pair dpd"_pair_dpd.html.
|
|
|
|
Fix {mvv/edpd} updates the per-atom temperature, in addition to
|
|
position and velocity, and must be used with the "pair_style
|
|
edpd"_pair_meso.html command.
|
|
|
|
Fix {mvv/tdpd} updates the per-atom chemical concentration, in
|
|
addition to position and velocity, and must be used with the
|
|
"pair_style tdpd"_pair_meso.html command.
|
|
|
|
:line
|
|
|
|
[Restart, fix_modify, output, run start/stop, minimize info:]
|
|
|
|
No information about this fix is written to "binary restart
|
|
files"_restart.html. None of the "fix_modify"_fix_modify.html options
|
|
are relevant to this fix. No global or per-atom quantities are stored
|
|
by this fix for access by various "output commands"_Howto_output.html.
|
|
No parameter of this fix can be used with the {start/stop} keywords of
|
|
the "run"_run.html command. This fix is not invoked during "energy
|
|
minimization"_minimize.html.
|
|
|
|
[Restrictions:]
|
|
|
|
This fix is part of the USER-MESO package. It is only enabled if
|
|
LAMMPS was built with that package. See the "Build
|
|
package"_Build_package.html doc page for more info.
|
|
|
|
[Related commands:]
|
|
|
|
"pair_style mdpd"_pair_meso.html, "pair_style edpd"_pair_meso.html,
|
|
"pair_style tdpd"_pair_meso.html
|
|
|
|
[Default:]
|
|
|
|
The default value for the optional {lambda} parameter is 0.5.
|
|
|
|
:line
|
|
|
|
:link(Groot2)
|
|
[(Groot)] Groot and Warren, J Chem Phys, 107: 4423-4435 (1997). DOI:
|
|
10.1063/1.474784
|
|
|