forked from lijiext/lammps
127 lines
5.5 KiB
Plaintext
127 lines
5.5 KiB
Plaintext
"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c
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:link(lws,http://lammps.sandia.gov)
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:link(ld,Manual.html)
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:link(lc,Section_commands.html#comm)
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:line
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region command :h3
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[Syntax:]
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region ID style args keyword value ... :pre
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ID = user-assigned name for the region :ulb,l
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style = {block} or {cylinder} or {prism} or {sphere} or {union} or {intersect} :l
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{block} args = xlo xhi ylo yhi zlo zhi
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xlo,xhi,ylo,yhi,zlo,zhi = bounds of block in all
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dimensions (distance units)
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{cylinder} args = dim c1 c2 radius lo hi
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dim = {x} or {y} or {z} = axis of cylinder
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c1,c2 = coords of cylinder axis in other 2 dimensions (distance units)
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radius = cylinder radius (distance units)
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lo,hi = bounds of cylinder in dim (distance units)
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{prism} args = xlo xhi ylo yhi zlo zhi yxtilt zxtilt zytilt
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xlo,xhi,ylo,yhi,zlo,zhi = bounds of untilted prism in all
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dimensions (distance units)
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yxtilt = distance to shift upper y in x direction (distance units)
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zxtilt = distance to shift upper z in x direction (distance units)
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zytilt = distance to shift upper z in y direction (distance units)
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{sphere} args = x y z radius
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x,y,z = center of sphere (distance units)
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radius = radius of sphere (distance units)
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{union} args = N reg-ID1 reg-ID2 ...
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N = # of regions to follow, must be 2 or greater
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reg-ID1,reg-ID2, ... = IDs of regions to join together
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{intersect} args = N reg-ID1 reg-ID2 ...
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N = # of regions to follow, must be 2 or greater
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reg-ID1,reg-ID2, ... = IDs of regions to intersect :pre
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zero or more keyword/value pairs may be appended to the args :l
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keyword = {side} or {units} :l
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{side} value = {in} or {out}
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{in} = the region is inside the specified geometry
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{out} = the region is outside the specified geometry
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{units} value = {lattice} or {box}
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{lattice} = the geometry is defined in lattice units
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{box} = the geometry is defined in simulation box units :pre
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:ule
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[Examples:]
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region 1 block -3.0 5.0 INF 10.0 INF INF
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region 2 sphere 0.0 0.0 0.0 5 side out
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region void cylinder y 2 3 5 -5.0 INF units box
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region 1 prism 0 10 0 10 0 10 2 0 0
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region outside union 4 side1 side2 side3 side4 :pre
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[Description:]
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This command defines a geometric region of space. Various other
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commands use regions. For example, the region can be filled with
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atoms via the "create_atoms"_create_atoms.html command. Or the atoms
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in the region can be identified as a group via the "group"_group.html
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command, or deleted via the "delete_atoms"_delete_atoms.html command.
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The lo/hi values for {block} or {cylinder} or {prism} styles can be
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specified as INF which means they extend all the way to the global
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simulation box boundary. If a region is defined before the simulation
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box has been created (via "create_box"_create_box.html or
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"read_data"_read_data.html or "read_restart"_read_restart.html
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commands), then an INF parameter cannot be used.
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For style {cylinder}, the c1,c2 params are coordinates in the 2 other
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dimensions besides the cylinder axis dimension. For dim = x, c1/c2 =
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y/z; for dim = y, c1/c2 = x/z; for dim = z, c1/c2 = x/y. Thus the
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third example above specifes a cylinder with its axis in the
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y-direction located at x = 2.0 and z = 3.0, with a radius of 5.0, and
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extending in the y-direction from -5.0 to the upper box boundary.
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For style {prism}, a tilted block is defined. The bounds of the
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untilted axis-aligned block are specified in the same way as for the
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{block} style. A tilt factor for each dimension with respect to
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another dimension is also specified. If the lower xy face of the
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prism is initially a rectangle (untilted), then the yxtilt factor
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specifies how far the upper y edge of that face is shifted in the x
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direction (skewing that face, keeping the xy face a parallelogram). A
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plus or minus value can be chosen; 0.0 would be no tilt. Similarly,
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zxtilt and zytilt describe how far the upper xy face of the prism is
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translated in the x and y directions to further tilt the prism. The
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final prism shape remains a parallelipiped, with opposing pairs of the
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6 faces remaining parallel to each other.
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The {union} style creates a region consisting of the volume of all the
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listed regions combined. The {intesect} style creates a region
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consisting of the volume that is common to all the listed regions.
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The {side} keyword determines whether the region is considered to be
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inside or outside of the specified geometry. Using this keyword in
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conjunction with {union} and {intersect} regions, complex geometries
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can be built up. For example, if the interior of two spheres were
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each defined as regions, and a {union} style with {side} = out was
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constructed listing the region-IDs of the 2 spheres, the resulting
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region would be all the volume in the simulation box that was outside
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both of the spheres.
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The {units} keyword determines the meaning of the distance units used
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to define the region. A {box} value selects standard distance units
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as defined by the "units"_units.html command, e.g. Angstroms for units
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= real or metal. A {lattice} value means the distance units are in
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lattice spacings. The "lattice"_lattice.html command must have been
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previously used to define the lattice spacing.
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[Restrictions:] none
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A prism cannot be of 0.0 thickness in any dimension; use a small z
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thickness for 2d simulations. For 2d simulations, the zxtilt and
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zytilt parameters must be 0.0.
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[Related commands:]
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"lattice"_lattice.html, "create_atoms"_create_atoms.html,
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"delete_atoms"_delete_atoms.html, "group"_group.html
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[Default:]
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The option defaults are side = in and units = lattice.
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