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fix indent command

Syntax:

fix ID group-ID indent k keyword args ... 

Examples:

fix 1 all indent 10.0 sphere 0.0 0.0 15.0 3.0 vel 0.0 0.0 -1.0
fix 2 flow indent 10.0 cylinder z 0.0 0.0 10.0 units box 

Description:

Insert an indenter within a simulation box. The indenter repels all atoms that touch it, so it can be used to push into a material or as an obstacle in a flow.

The indenter can either be spherical or cylindrical. You must set one of those 2 keywords.

A spherical indenter exerts a force of magnitude

F(r) = - k (r - R)^2 

on each atom where k is the specified force constant, r is the distance from the atom to the center of the indenter, and R is the radius of the indenter. The force is repulsive and F(r) = 0 for r > R.

A cylindrical indenter exerts the same force, except that r is the distance from the atom to the center axis of the cylinder. The cylinder extends infinitely along its axis.

If the vel keyword is specified, the center (or axis) of the spherical (or cylindrical) indenter will move during the simulation, based on its initial (x,y,z) position and the specified (vx,vy,vz).

The units keyword determines the meaning of the distance units used to define the indenter. 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. The lattice command must first be used to define a lattice. Note that the units choice affects not only the indenter's physical geometry, but also its velocity and force constant since they are defined in terms of distance as well.

Restrictions: none

Related commands: none

Default:

The option defaults are vel = 0,0,0 and units = lattice.