lammps/doc/angle_hybrid.txt

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angle_style hybrid command :h3

[Syntax:]

angle_style hybrid style1 style2 ... :pre

style1,style2 = list of one or more angle styles :ul

[Examples:]

angle_style hybrid harmonic cosine
angle_coeff 1 harmonic 80.0 30.0
angle_coeff 2* cosine 50.0  :pre

[Description:]

The {hybrid} style enables the use of multiple angle styles in one
simulation.  An angle style is assigned to each angle type.  For
example, angles in a polymer flow (of angle type 1) could be computed
with a {harmonic} potential and angles in the wall boundary (of angle
type 2) could be computed with a {cosine} potential.  The assignment
of angle type to style is made via the "angle_coeff"_angle_coeff.html
command or in the data file.

In the angle_coeff commands, the name of an angle style must be added
after the angle type, with the remaining coefficients being those
appropriate to that style.  In the example above, the 2 angle_coeff
commands set angles of angle type 1 to be computed with a {harmonic}
potential with coefficients 80.0, 30.0 for K, theta0.  All other angle
types (2-N) are computed with a {cosine} potential with coefficient
50.0 for K.

If angle coefficients are specified in the data file read via the
"read_data"_read_data.html command, then the same rule applies.
E.g. "harmonic" or "cosine", must be added after the angle type, for each
line in the "Angle Coeffs" section, e.g.

Angle Coeffs :pre

1 harmonic 80.0 30.0
2 cosine 50.0
... :pre

If {class2} is one of the angle hybrid styles, the same rule holds for
specifying additional BondBond (and BondAngle) coefficients either via
the input script or in the data file.  I.e. {class2} must be added to
each line after the angle type.  For lines in the BondBond (or
BondAngle) section of the data file for angle types that are not
{class2}, you must use an angle style of {skip} as a placeholder, e.g.

BondBond Coeffs :pre

1 skip
2 class2 3.6512 1.0119 1.0119
... :pre

Note that it is not necessary to use the angle style {skip} in the
input script, since BondBond (or BondAngle) coefficients need not be
specified at all for angle types that are not {class2}.

An angle style of {none} with no additional coefficients can be used
in place of an angle style, either in a input script angle_coeff
command or in the data file, if you desire to turn off interactions
for specific angle types.

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[Restrictions:]

This angle style can only be used if LAMMPS was built with the
MOLECULAR package (which it is by default).  See the "Making
LAMMPS"_Section_start.html#start_3 section for more info on packages.

Unlike other angle styles, the hybrid angle style does not store angle
coefficient info for individual sub-styles in a "binary restart
files"_restart.html.  Thus when retarting a simulation from a restart
file, you need to re-specify angle_coeff commands.

[Related commands:]

"angle_coeff"_angle_coeff.html

[Default:] none