81 lines
2.6 KiB
Plaintext
81 lines
2.6 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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compute pe command :h3
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[Syntax:]
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compute ID group-ID pe keyword ... :pre
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ID, group-ID are documented in "compute"_compute.html command
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pe = style name of this compute command
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zero or more keywords may be appended
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keyword = {pair} or {bond} or {angle} or {dihedral} or {improper} or {kspace} or {fix} :ul
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[Examples:]
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compute 1 all pe
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compute molPE all pe bond angle dihedral improper :pre
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[Description:]
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Define a computation that calculates the potential energy of the
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entire system of atoms. The specified group must be "all". See the
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"compute pe/atom"_compute_pe_atom.html command if you want per-atom
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energies. These per-atom values could be summed for a group of atoms
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via the "compute reduce"_compute_reduce.html command.
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The energy is calculated by the various pair, bond, etc potentials
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defined for the simulation. If no extra keywords are listed, then the
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potential energy is the sum of pair, bond, angle, dihedral, improper,
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kspace (long-range), and fix energy. I.e. it is as if all the
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keywords were listed. If any extra keywords are listed, then only
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those components are summed to compute the potential energy.
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The Kspace contribution requires 1 extra FFT each timestep the energy
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is calculated, if using the PPPM solver via the "kspace_style
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pppm"_kspace_style.html command. Thus it can increase the cost of the
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PPPM calculation if it is needed on a large fraction of the simulation
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timesteps.
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Various fixes can contribute to the total potential energy of the
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system if the {fix} contribution is included. See the doc pages for
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"individual fixes"_fix.html for details of which ones compute a
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potential energy.
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NOTE: The "fix_modify energy yes"_fix_modify.html command must also be
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specified if a fix is to contribute potential energy to this command.
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A compute of this style with the ID of "thermo_pe" is created when
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LAMMPS starts up, as if this command were in the input script:
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compute thermo_pe all pe :pre
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See the "thermo_style" command for more details.
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:line
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[Output info:]
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This compute calculates a global scalar (the potential energy). This
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value can be used by any command that uses a global scalar value from
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a compute as input. See "Section
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6.15"_Section_howto.html#howto_15 for an overview of LAMMPS output
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options.
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The scalar value calculated by this compute is "extensive". The
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scalar value will be in energy "units"_units.html.
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[Restrictions:] none
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[Related commands:]
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"compute pe/atom"_compute_pe_atom.html
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[Default:] none
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