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### shape command

Syntax:

    mass I x y z

- I = atom type (see asterik form below)
- x = x diameter
- y = y diameter
- z = z diameter

Examples:

    shape 1 1.0 1.0 1.0
    shape * 3.0 1.0 1.0
    shape 2* 3.0 1.0 1.0

Description:

Set the shape for all atoms of one or more atom types. Shape values can also be set in the read_data data file. See the units command for what distance units to use.

Currently, only atom_style dipole and atom_style ellipsoid require that shapes be set.

Dipoles use the atom shape to compute a moment of inertia for rotational energy. Only the 1st component of the shape is used since the particles are assumed to be spherical. The value of the first component should be the same as the Lennard-Jones sigma value defined in the dipole pair potential, i.e. in pair_style dipole.

Ellipsoids use the atom shape to compute a generalized inertia tensor. For example, a shape setting of 3.0 1.0 1.0 defines a particle 3x longer in x than in y or z and with a circular cross-section in yz. Ellipsoids that are spherical can be defined by setting all 3 shape components the same.

The I index can be specified in one of two ways. An explicit numeric value can be used, as in the 1st example above. Or a wild-card asterik can be used to set the mass for multiple atom types. This takes the form "*" or "*n" or "n*" or "m*n". If N = the number of atom types, then an asterik with no numeric values means all types from 1 to N. A leading asterik means all types from 1 to n (inclusive). A trailing asterik means all types from n to N (inclusive). A middle asterik means all types from m to n (inclusive).

A line in a data file that specifies shape uses the same format as the arguments of the shape command in an input script, except that no wild-card asterik can be used. For example, under the "Shapes" section of a data file, the line that corresponds to the 1st example above would be listed as

    1 1.0 1.0 1.0

Restrictions:

This command must come after the simulation box is defined by a read_data, read_restart, or create_box command.

All shapes must be defined before a simulation is run (if the atom style requires shapes be set).

Related commands: none

Default: none