NAME

       LAMMPS - Molecular Dynamics Simulator.

SYNOPSIS

       lmp -in <input file> [OPTIONS] ...

       or

       mpirun -np 2 lmp <input file> [OPTIONS] ...

       or

       lmp -r2data file.restart file.data

DESCRIPTION

       LAMMPS  is a classical molecular dynamics code, and an acronym for Large-scale Atomic/Molecular Massively
       Parallel Simulator.  LAMMPS has potentials for soft materials (bio-molecules, polymers)  and  solid-state
       materials  (metals,  semiconductors)  and  coarse-grained  or mesoscopic systems. It can be used to model
       atoms or, more generically, as a parallel particle simulator at the atomic, meso, or continuum scale.

       See https://lammps.sandia.gov/ for more information and documentation.

EXECUTABLE NAME

       The LAMMPS executable can have  different  names  depending  on  how  it  was  configured,  compiled  and
       installed.  It  will  be  either lmp or lmp_<machine name>.  The <machine name> suffix corresponds to the
       (machine specific) makefile used to compile LAMMPS  when  using  the  conventional  build  process.  When
       building  LAMMPS  using  CMake  this  <machine name> parameter can be chosen arbitrarily at configuration
       time, but more common is to just use lmp without a suffix. In this manpage we will use lmp  to  represent
       any of those names.

OPTIONS

       -h or -help
              Print  a  brief  help summary and a list of settings and options compiled into this executable. It
              also explicitly lists all LAMMPS styles (atom_style, fix, compute,  pair_style,  bond_style,  etc)
              available  in  the  specific  executable.  This  can  tell  you if the command you want to use was
              included via the appropriate package at compile time.  LAMMPS will print the info and  immediately
              exit if this switch is used.

       -e or -echo
              Set  the  style  of command echoing. The style can be none or screen or log or both.  Depending on
              the style, each command read from the input script will be echoed to the  screen  and/or  logfile.
              This can be useful to figure out which line of your script is causing an input error.  The default
              value is log.

       -i <input file> or -in <input file>
              Specify  a  file  to  use as an input script. If it is not specified, LAMMPS reads its script from
              standard input. This is a required switch when running LAMMPS in multi-partition mode.

       -k on/off [keyword value] or -kokkos on/off [keyword value]
              Enable or disable general KOKKOS support, as provided by the KOKKOS package.  Even  if  LAMMPS  is
              built  with  this  package,  this  switch  must be set to on to enable running with KOKKOS-enabled
              styles. More details on this switch and  its  optional  keyword  value  pairs  are  discussed  at:
              https://lammps.sandia.gov/doc/Run_options.html

       -l <log file> or -log <log file>
              Specify  a log file for LAMMPS to write status information to.  The default value is "log.lammps".
              If the file name "none" is used, LAMMPS will not write a log file. In  multi-partition  mode  only
              some  high-level  all-partition  information is written to the "<log file>" file, the remainder is
              written in a per-partition file "<log file>.N" with "N" being  the  respective  partition  number,
              unless overridden by the -plog flag (see below).

       -m <number> or -mpicolor <number>
              If used, this must be the first command-line argument after the LAMMPS executable name. It is only
              used  when  LAMMPS  is  launched  by  an  mpirun  command  which  also  launches one or more other
              executable(s) at the same time.  LAMMPS and the other executable(s) perform  an  MPI_Comm_split(),
              each with their own different colors, to split the MPI_COMM_WORLD communicator for each executable
              to  the  subset of processors they are supposed to be actually running on. Currently, this is only
              used in LAMMPS to perform client/server messaging with another application.   LAMMPS  can  act  as
              either a client or server (or both).

       -nc or -nocite
              Disable  writing  the  "log.cite"  file  which is normally written to list references for specific
              cite-able features used during a LAMMPS run.

       -pk <style> [options] or -package <style> [options]
              Invoke the package command with <style> and optional arguments.  The syntax is the same as if  the
              command  appeared  in  an input script.  For example "-pk gpu 2" is the same as "package gpu 2" in
              the input script. The possible styles and options are discussed  in  the  LAMMPS  manual  for  the
              "package"  command. This switch can be used multiple times, e.g. to set options for the USER-INTEL
              and USER-OMP packages when used together. Along with the "-sf" or  "-suffix"  switch,  this  is  a
              convenient mechanism for invoking accelerator packages and their options without having to edit an
              input script.

       -p or -partition
              Invoke  LAMMPS  in  multi-partition mode. Without this, LAMMPS uses all P processors allocated via
              MPI to run a single simulation.  If this switch is used, the P processors are split into  separate
              partitions  and  each  partition  runs its own simulation. The arguments to the switch specify the
              number of processors in each partition.  Arguments of the form "MxN" mean M partitions, each  with
              N  processors.   Arguments  of the form "N" mean a single partition with N processors.  The sum of
              processors in all partitions must be equal P. Thus  the  command  “-partition  8x2  4  5”  has  10
              partitions and runs on a total of 25 processors.  Running with multiple partitions is required for
              multi-replica simulations, where each replica runs on on one or more few processors.

       -pl <basename> or -plog <basename>
              Specify  the  base name for the per-partition log files in multi-partition runs, where partition N
              writes log information to <basename>.N.  If basename is set to "none", then no  per-partition  log
              files are created.  This overrides the name specified in the -log command-line option.

       -ps <basename> or -pscreen <basename>
              Specify  the base name for the per-partition screen files in multi-partition runs, where partition
              N writes screen output to <basename>.N.  If basename is  set  to  "none",  then  no  per-partition
              screen files are created.  The default value is "screen" or whatever is set by the -screen flag.

       -r2data <restart file> [remap] <data file> or
              -restart2data  <restart  file>  [remap]  <data  file> Convert <restart file> previously written by
              LAMMPS into a data file and immediately exit. This option has replaced the  external  restart2data
              executable. Following <restart file> argument, the optional word "remap" may be used. This has the
              same effect like adding it to a "read_restart" command.  The syntax following the <data file> name
              is  identical  to  the arguments of the "write_data" command. See the LAMMPS manual for details on
              either of the two commands.

       -r2dump <restart file> [remap] <dump file> or
              -restart2dump <restart file> [remap] <dump file> Convert  <restart  file>  previously  written  by
              LAMMPS into a dump file and immediately exit. Following <restart file> argument, the optional word
              "remap"  may  be  used.  This has the same effect like adding it to a "read_restart" command.  The
              syntax following the <dump file> name is identical to the arguments of the "dump" command. See the
              LAMMPS manual for details on either of the two commands.

       -sc <file name> or -screen <file name>
              Specify a file for LAMMPS to write its screen  information  to.  By  default,  this  will  be  the
              standard  output.  If  <file  name> is "none", (most) screen output will be suppressed.  In multi-
              partition mode only some high-level all-partition information is written to the screen  or  "<file
              name>"  file,  the remainder is written in a per-partition file "screen.N" or "<file name>.N" with
              "N" being the respective partition number, and unless overridden by the -pscreen flag (see above).

       -sf <suffix> or -suffix <suffix>
              Use variants of various styles in the input, if they exist.  This  is  achieved  by  transparently
              trying to convert a style named <my/style> into <my/style/suffix> if that latter style exists, but
              otherwise  fall  back  to  the  former. The most useful suffixes are  "gpu", "intel", "kk", "omp",
              "opt", or "hybrid". These refer to styles from optional packages that LAMMPS can  be  built  with.
              The  hybrid  suffix  is  special, as it enables, having two suffixes tried (e.g. first "intel" and
              then "omp") and thus requires two arguments. Along with the "-package" command-line  switch,  this
              is  a convenient mechanism for invoking styles from accelerator packages and setting their options
              without having to edit an input script.

              See https://lammps.sandia.gov/doc/Run_options.html  for  additional  details  and  discussions  on
              command-line options.

LAMMPS BASICS

       LAMMPS  executes by reading commands from a input script (text file), one line at a time.  When the input
       script ends, LAMMPS exits.  Each command causes LAMMPS to take some action.  It  may  set  or  change  an
       internal,  read  and parse a file, or run a simulation.  Most commands have default settings, which means
       you only need to use the command if you wish to change the default.

       The ordering of commands in an input script is usually not very important unless a command like "run"  is
       encountered,  which  starts some calculation using the current internal state. Also, if a "pair_style" or
       "bond_style" other similar style command is issued that has a different name  from  what  was  previously
       active, it will replace the previous style and wipe out all corresponding "pair_coeff" or "bond_coeff" or
       equivalent  settings.   Some  commands  are  only valid when they follow other commands.  For example you
       cannot set the temperature of a group of atoms until atoms have been defined and a group command is  used
       to  define  which atoms belong to the group of a given name. Sometimes command B will use values that can
       be set by command A. This means command A must precede command B in the input to have the desired effect.
       Some commands must be issued before the simulation box is defined and others can only  be  issued  after.
       Many  input  script  errors  are  detected  by  LAMMPS  and  an ERROR or WARNING message is printed.  The
       documentation for each command lists restrictions on how the command can be  used,  and  the  chapter  on
       errors in the LAMMPS manual gives some additional information about error messages, if possible.

COPYRIGHT

       © 2003--2019 Sandia Corporation

       This  package  is  free  software;  you  can  redistribute it and/or modify it under the terms of the GNU
       General Public License version 2 as published by the Free Software Foundation.

       This package is distributed in the hope that it will be useful, but WITHOUT ANY  WARRANTY;  without  even
       the  implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
       License for more details.

       On  Debian  systems,  the  complete  text  of  the  GNU  General  Public  License   can   be   found   in
       `/usr/share/common-licenses/GPL-2'.

2019-11-20                                      20 November 2019                                       LAMMPS(1)