forked from lijiext/lammps
76 lines
2.7 KiB
Plaintext
76 lines
2.7 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
|
||
|
|
|
||
|
|
displace_atoms command :h3
|
||
|
|
|
||
|
|
[Syntax:]
|
||
|
|
|
||
|
|
displace_atoms group-ID style args keyword value ... :pre
|
||
|
|
|
||
|
|
group-ID = ID of group of atoms to displace :ulb,l
|
||
|
|
style = {move} or {ramp} :l
|
||
|
|
{move} args = delx dely delz
|
||
|
|
delx,dely,delz = distance to displace in each dimension (distance units)
|
||
|
|
{ramp} args = ddim dlo dhi dim clo chi
|
||
|
|
ddim = {x} or {y} or {z}
|
||
|
|
dlo,dhi = displacement distance between dlo and dhi (distance units)
|
||
|
|
dim = {x} or {y} or {z}
|
||
|
|
clo,chi = lower and upper bound of domain to displace (distance units) :pre
|
||
|
|
zero or more keyword/value pairs may be appended to the args :l
|
||
|
|
keyword = {units}
|
||
|
|
value = {box} or {lattice} :pre
|
||
|
|
:ule
|
||
|
|
|
||
|
|
[Examples:]
|
||
|
|
|
||
|
|
displace_atoms top move 0 -5 0 units box
|
||
|
|
displace_atoms flow ramp x 0.0 5.0 y 2.0 20.5 :pre
|
||
|
|
|
||
|
|
[Description:]
|
||
|
|
|
||
|
|
Displace a group of atoms. This can be useful to move atoms a large
|
||
|
|
distance before beginning a simulation. For example, in a shear
|
||
|
|
simulation, an initial strain can be imposed on the system. Or two
|
||
|
|
groups of atoms can be brought into closer proximity.
|
||
|
|
|
||
|
|
The {move} style displaces the group of atoms by the specified 3d
|
||
|
|
distance. The {ramp} style displaces atoms a variable amount in one
|
||
|
|
dimension depending on the atom's coordinate in a (possibly) different
|
||
|
|
dimension. For example, the second example command displaces atoms in
|
||
|
|
the x-direction an amount between 0.0 and 5.0 distance units. Each
|
||
|
|
atom's displacement depends on the fractional distance its y
|
||
|
|
coordinate is between 2.0 and 20.5. Atoms with y-coordinates outside
|
||
|
|
those bounds will be moved the minimum (0.0) or maximum (5.0) amount.
|
||
|
|
|
||
|
|
Distance units for the displacement are determined by the setting of
|
||
|
|
{box} or {lattice} for the {units} keyword. {Box} means distance
|
||
|
|
units as defined by the "units"_units.html command - e.g. Angstroms
|
||
|
|
for {real} units. {Lattice} means to use lattice spacings as defined
|
||
|
|
by the "lattice"_lattice.html command. The default is to use lattice
|
||
|
|
units.
|
||
|
|
|
||
|
|
Care should be taken not to move atoms on top of other atoms. After
|
||
|
|
the move, atoms are remapped to the periodic simulation box. In
|
||
|
|
parallel, atoms should not be moved so far that they cross more than
|
||
|
|
one processor's sub-domain, else they may be lost. If this is a
|
||
|
|
problem, successive displace_atom commands can be used to move atoms a
|
||
|
|
large distance.
|
||
|
|
|
||
|
|
[Restrictions:]
|
||
|
|
|
||
|
|
This command requires inter-processor communication to migrate atoms
|
||
|
|
once they have been displaced. This means that your system must be
|
||
|
|
ready to perform a simulation before using this command (force fields
|
||
|
|
setup, atom masses set, etc).
|
||
|
|
|
||
|
|
[Related commands:] none
|
||
|
|
|
||
|
|
[Default:]
|
||
|
|
|
||
|
|
The option defaults are units = lattice.
|