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# 3.8. Compute styles

Classes that compute scalar and vector quantities like temperature and the pressure tensor, as well as classes that compute per-atom quantities like kinetic energy and the centro-symmetry parameter are derived from the Compute class. New styles can be created to add new calculations to LAMMPS.

Compute_temp.cpp is a simple example of computing a scalar temperature. Compute_ke_atom.cpp is a simple example of computing per-atom kinetic energy.

Here is a brief description of methods you define in your new derived class. See compute.h for details.

init |
perform one time setup (required) |

init_list |
neighbor list setup, if needed (optional) |

compute_scalar |
compute a scalar quantity (optional) |

compute_vector |
compute a vector of quantities (optional) |

compute_peratom |
compute one or more quantities per atom (optional) |

compute_local |
compute one or more quantities per processor (optional) |

pack_comm |
pack a buffer with items to communicate (optional) |

unpack_comm |
unpack the buffer (optional) |

pack_reverse |
pack a buffer with items to reverse communicate (optional) |

unpack_reverse |
unpack the buffer (optional) |

remove_bias |
remove velocity bias from one atom (optional) |

remove_bias_all |
remove velocity bias from all atoms in group (optional) |

restore_bias |
restore velocity bias for one atom after remove_bias (optional) |

restore_bias_all |
same as before, but for all atoms in group (optional) |

pair_tally_callback |
callback function for |

memory_usage |
tally memory usage (optional) |

Tally-style computes are a special case, as their computation is done
in two stages: the callback function is registered with the pair style
and then called from the Pair::ev_tally() function, which is called for
each pair after force and energy has been computed for this pair. Then
the tallied values are retrieved with the standard compute_scalar or
compute_vector or compute_peratom methods. The compute styles in the TALLY package
provide *examples* for utilizing this mechanism.