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< CENTER > < A HREF = "http://lammps.sandia.gov" > LAMMPS WWW Site< / A > - < A HREF = "Manual.html" > LAMMPS Documentation< / A > - < A HREF = "Section_commands.html#comm" > LAMMPS Commands< / A >
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< HR >
< H3 > atom_style command
< / H3 >
< P > < B > Syntax:< / B >
< / P >
< PRE > atom_style style args
< / PRE >
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< UL > < LI > style = < I > angle< / I > or < I > atomic< / I > or < I > bond< / I > or < I > charge< / I > or < I > dpd< / I > or < I > full< / I > or < I > granular< / I > or < I > molecular< / I > or < I > hybrid< / I >
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< / UL >
< PRE > args = none for any style except < I > hybrid< / I >
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< I > hybrid< / I > args = list of one or more sub-styles
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< / PRE >
< P > < B > Examples:< / B >
< / P >
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< PRE > atom_style atomic
atom_style bond
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atom_style full
atom_style hybrid charge bond
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< P > < B > Description:< / B >
< / P >
< P > Define what style of atoms to use in a simulation. This determines
what attributes are associated with the atoms. This command must be
used before a simulation is setup via a < A HREF = "read_data.html" > read_data< / A > ,
< A HREF = "read_restart.html" > read_restart< / A > , or < A HREF = "create_box.html" > create_box< / A >
command.
< / P >
< P > Once a style is assigned, it cannot be changed, so use a style general
enough to encompass all attributes. E.g. with style < I > bond< / I > , angular
terms cannot be used or added later to the model. It is OK to use a
style more general than needed, though it may be slightly inefficient.
< / P >
< P > The choice of style affects what quantities are stored by each atom,
what quantities are communicated between processors to enable forces
to be computed, and what quantities are listed in the data file read
by the < A HREF = "read_data.html" > read_data< / A > command.
< / P >
< P > These are the attributes of each style. All styles store coordinates,
velocities, atom IDs and types.
< / P >
< UL > < LI > < I > angle< / I > = bonds and angles - e.g. bead-spring polymers with stiffness
< LI > < I > atomic< / I > = only the default values
< LI > < I > bond< / I > = bonds - e.g. bead-spring polymers
< LI > < I > charge< / I > = charge
< LI > < I > dpd< / I > = default values, also communicates velocities
< LI > < I > molecular< / I > = bonds, angles, dihedrals, impropers - e.g. all-atom polymers
< LI > < I > full< / I > = molecular + charge - e.g. biomolecules, charged polymers
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< LI > < I > granular< / I > = granular atoms with rotational properties
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< / UL >
< P > Typical simulations with a single pair potential will use only one of
these styles. For cases where multiple pair potentials will be used
(see the < A HREF = "pair_style.html" > pair_style< / A > < I > hybrid< / I > command), it may be
necessary to use multiple atom styles. Another example is doing a DPD
simulations with bonds or angles. In these cases the < I > hybrid< / I > style
can be used to list multiple atom styles. Atoms will then store and
communicate the union of all quantities implied by the individual
styles.
< / P >
< P > LAMMPS can be extended with new atom styles; see < A HREF = "Section_modify.html" > this
section< / A > .
< / P >
< P > < B > Restrictions:< / B >
< / P >
< P > This command cannot be used after the simulation box is defined by a
< A HREF = "read_data.html" > read_data< / A > or < A HREF = "create_box.html" > create_box< / A > command.
< / P >
< P > The < I > angle< / I > , < I > bond< / I > , < I > full< / I > , and < I > molecular< / I > styles are part of the
"molecular" package. The < I > granular< / I > style is part of the "granular"
package. The < I > dpd< / I > style is part of the "dpd" package. They are only
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enabled if LAMMPS was built with that package. See the < A HREF = "Section_start.html#2_3" > Making
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LAMMPS< / A > section for more info.
< / P >
< P > < B > Related commands:< / B >
< / P >
< P > < A HREF = "read_data.html" > read_data< / A > , < A HREF = "pair_style.html" > pair_style< / A >
< / P >
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< P > < B > Default:< / B >
< / P >
< P > atom_style atomic
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< / P >
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