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Aidan Thompson
2025-01-11 12:32:05 -07:00
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doc/src/pair_hybrid.rst
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@ -78,7 +78,7 @@ styles enable the use of multiple pair styles in one simulation. With
the *hybrid* style, exactly one pair style is assigned to each pair of
atom types. With the *hybrid/overlay* and *hybrid/scaled* styles, one
or more pair styles can be assigned to each pair of atom types. With
the hybrid/molecular style, pair styles are assigned to either intra-
the *hybrid/molecular* style, pair styles are assigned to either intra-
or inter-molecular interactions.
The assignment of pair styles to type pairs is made via the
@ -114,16 +114,26 @@ restrictions discussed below.
If the *hybrid/scaled* style is used instead of *hybrid/overlay*,
contributions from sub-styles are weighted by their scale factors, which
may be fractional or even negative. Furthermore the scale factors may
be variables that may change during a simulation. This enables
may be fractional or even negative. Furthermore the scale factor for
each sub-style may a constant, an *equal* style variable, or an *atom*
style variable. Variable scale factors may change during the simulation.
Different sub-styles may use different scale factor styles.
In the case of a sub-style scale factor that is an *atom* style variable,
the force contribution to each atom from that sub-style is weighted
by the value of the variable for that atom, while the contribution
from that sub-style to the global potential energy is zero.
All other contributions to the per-atom energy, per-atom
virial, and global virial (if not obtained from forces)
from that sub-style are zero.
This enables
switching smoothly between two different pair styles or two different
parameter sets during a run in a similar fashion as could be done
with :doc:`fix adapt <fix_adapt>` or :doc:`fix alchemy <fix_alchemy>`.
All pair styles that will be used are listed as "sub-styles" following
the *hybrid* or *hybrid/overlay* keyword, in any order. In case of the
*hybrid/scaled* pair style, each sub-style is prefixed with a scale
factor. The scale factor is either a floating point number or an equal
factor. The scale factor is either a floating point number or an
*equal* or *atom*
style (or equivalent) variable. Each sub-style's name is followed by
its usual arguments, as illustrated in the examples above. See the doc
pages of the individual pair styles for a listing and explanation of the
@ -374,7 +384,7 @@ between all atoms of types 1,3,4 will be computed by that potential.
Pair_style hybrid allows interactions between type pairs 2-2, 1-2,
2-3, 2-4 to be specified for computation by other pair styles. You
could even add a second interaction for 1-1 to be computed by another
pair style, assuming pair_style hybrid/overlay is used.
pair style, assuming pair_style *hybrid/overlay* is used.
But you should not, as a general rule, attempt to exclude the many-body
interactions for some subset of the type pairs within the set of 1,3,4
@ -414,7 +424,7 @@ passed to the Tersoff potential, which means it would compute no
3-body interactions containing both type 1 and 2 atoms.
Here is another example to use 2 many-body potentials together in an
overlapping manner using hybrid/overlay. Imagine you have CNT (C atoms)
overlapping manner using *hybrid/overlay*. Imagine you have CNT (C atoms)
on a Si surface. You want to use Tersoff for Si/Si and Si/C
interactions, and AIREBO for C/C interactions. Si atoms are type 1; C
atoms are type 2. Something like this will work: