Syntax:
region ID style args keyword value ...
rectangle args = xlo xhi ylo yhi zlo zhi xlo,xhi,ylo,yhi,zlo,zhi = bounds of block in all dimensions (distance units) sphere args = x y z radius x,y,z = center of sphere (distance units) radius = radius of sphere (distance units) cylinder args = dim c1 c2 radius lo hi dim = x or y or z = axis of cylinder c1,c2 = coords of cylinder axis in other 2 dimensions (distance units) radius = cylinder radius (distance units) lo,hi = bounds of cylinder in dim (distance units)
side value = in or out in = the region is inside the specified geometry out = the region is outside the specified geometry units value = lattice or box lattice = the geometry is defined in lattice units box = the geometry is defined in simulation box units
Examples:
region 1 block -3.0 5.0 INF 10.0 INF INF region 2 sphere 0.0 0.0 0.0 5 side out region void cylinder y 2 3 5 -5.0 INF units box
Description:
This command defines a geometric region of space. Various other commands use regions. For example, the region can be filled with atoms via the create_atoms command. Or the atoms in the region can be identified as a group via the group command, or deleted via the delete_atoms command.
The lo/hi values for rectangle or cylinder styles can be specified as INF which means they extend all the way to the global simulation box boundary. If a region is defined before the simulation box has been created (via create_box or read_data or read_restart commands), then an INF parameter cannot be used.
For region cylinder, the c1,c2 params are coordinates in the 2 other dimensions besides the cylinder axis dimension. For dim = x, c1/c2 = y/z; for dim = y, c1/c2 = x/z; for dim = z, c1/c2 = x/y. Thus the third example above specifes a cylinder with its axis in the y-direction located at x = 2.0 and z = 3.0, with a radius of 5.0, and extending in the y-direction from -5.0 to the upper box boundary.
The side keyword determines whether the region is considered to be inside or outside of the specified geometry.
The units keyword determines the meaning of the distance units used to defined the region. A box value selects standard distance units as defined by the units command. E.g. Angstroms for units = real or metal. A lattice value means the distance units are in cubic lattice spacings. See the lattice must first be used to define a lattice.
Restrictions: none
Related commands:
lattice, create_atoms, delete_atoms, group
Default:
The option defaults are side = in and units = lattice.