forked from lijiext/lammps
96 lines
3.2 KiB
Plaintext
96 lines
3.2 KiB
Plaintext
"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c
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:link(lws,http://lammps.sandia.gov)
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:link(ld,Manual.html)
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:link(lc,Section_commands.html#comm)
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:line
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dihedral_style command :h3
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[Syntax:]
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dihedral_style style :pre
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style = {none} or {hybrid} or {charmm} or {class2} or {harmonic} or {helix} or \
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{multi/harmonic} or {opls} :ul
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[Examples:]
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dihedral_style harmonic
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dihedral_style multi/harmonic
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dihedral_style hybrid harmonic charmm :pre
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[Description:]
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Set the formula(s) LAMMPS uses to compute dihedral interactions
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between quadruplets of atoms, which remain in force for the duration
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of the simulation. The list of dihedral quadruplets is read in by a
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"read_data"_read_data.html or "read_restart"_read_restart.html command
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from a data or restart file.
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Hybrid models where dihedrals are computed using different dihedral
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potentials can be setup using the {hybrid} dihedral style.
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The coefficients associated with a dihedral style can be specified in a
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data or restart file or via the "dihedral_coeff"_dihedral_coeff.html command.
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In the formulas listed for each dihedral style, {phi} is the torsional
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angle defined by the quadruplet of atoms.
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Note that when both a dihedral and pair style is defined, the
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"special_bond"_special_bond.html command often needs to be used to
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turn off (or weight) the pairwise interactions that would otherwise
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exist between the 4 bonded atoms.
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Here are some important points to take note of when defining the
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LAMMPS dihedral coefficients in the formulas that follow so that they
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are compatible with other force fields:
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The LAMMPS convention is that the trans position = 180 degrees, while
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in some force fields trans = 0 degrees. :ulb,l
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Some force fields reverse the sign convention on {d}. :l
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Some force fields divide/multiply {K} by the number of multiple
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torsions that contain the j-k bond in an i-j-k-l torsion. :l
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Some force fields let {n} be positive or negative which corresponds to
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{d} = 1 or -1 for the harmonic style. :ule,l
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:line
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Here is an alphabetic list of dihedral styles defined in LAMMPS. Click on
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the style to display the formula it computes and coefficients
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specified by the associated "dihedral_coeff"_dihedral_coeff.html command:
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"dihedral_style none"_dihedral_style_none.html - turn off dihedral interactions
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"dihedral_style hybrid"_dihedral_style_hybrid.html - define multiple styles of dihedral interactions :ul
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"dihedral_style charmm"_dihedral_style_charmm.html - CHARMM dihedral
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"dihedral_style class2"_dihedral_style_class2.html - COMPASS (class 2) dihedral
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"dihedral_style harmonic"_dihedral_style_harmonic.html - harmonic dihedral
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"dihedral_style helix"_dihedral_style_helix.html - helix dihedral
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"dihedral_style multi/harmonic"_dihedral_style_multi_harmonic.html - multi-harmonic dihedral
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"dihedral_style opls"_dihedral_style_opls.html - OPLS dihedral :ul
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:line
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[Restrictions:]
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Dihedral styles can only be set for atom styles that allow dihedrals
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to be defined.
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Dihedral styles are part of the "molecular" package or other packages
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as noted in their documentation. They are only enabled if LAMMPS was
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built with that package. See the "Making
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LAMMPS"_Section_start.html#2_2 section for more info.
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[Related commands:]
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"dihedral_coeff"_dihedral_coeff.html
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[Default:]
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dihedral_style none
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