10. Auxiliary tools

LAMMPS is designed to be a computational kernel for performing molecular dynamics computations. Additional pre- and post-processing steps are often necessary to setup and analyze a simulation. A list of such tools can be found on the LAMMPS webpage at these links:

The last link for Pizza.py is a Python-based tool developed at Sandia which provides tools for doing setup, analysis, plotting, and visualization for LAMMPS simulations.

Additional tools included in the LAMMPS distribution are described on this page.

Note that many users write their own setup or analysis tools or use other existing codes and convert their output to a LAMMPS input format or vice versa. The tools listed here are included in the LAMMPS distribution as examples of auxiliary tools. Some of them are not actively supported by the LAMMPS developers, as they were contributed by LAMMPS users. If you have problems using them, we can direct you to the authors.

The source code for each of these codes is in the tools sub-directory of the LAMMPS distribution. There is a Makefile (which you may need to edit for your platform) which will build several of the tools which reside in that directory. Most of them are larger packages in their own sub-directories with their own Makefiles and/or README files.

10.2. Post-processing tools


















10.4. Tool descriptions

10.4.1. amber2lmp tool

The amber2lmp sub-directory contains two Python scripts for converting files back-and-forth between the AMBER MD code and LAMMPS. See the README file in amber2lmp for more information.

These tools were written by Keir Novik while he was at Queen Mary University of London. Keir is no longer there and cannot support these tools which are out-of-date with respect to the current LAMMPS version (and maybe with respect to AMBER as well). Since we don’t use these tools at Sandia, you will need to experiment with them and make necessary modifications yourself.

10.4.2. binary2txt tool

The file binary2txt.cpp converts one or more binary LAMMPS dump file into ASCII text files. The syntax for running the tool is

binary2txt file1 file2 ...

which creates file1.txt, file2.txt, etc. This tool must be compiled on a platform that can read the binary file created by a LAMMPS run, since binary files are not compatible across all platforms.

10.4.3. ch2lmp tool

The ch2lmp sub-directory contains tools for converting files back-and-forth between the CHARMM MD code and LAMMPS.

They are intended to make it easy to use CHARMM as a builder and as a post-processor for LAMMPS. Using charmm2lammps.pl, you can convert a PDB file with associated CHARMM info, including CHARMM force field data, into its LAMMPS equivalent. Support for the CMAP correction of CHARMM22 and later is available as an option. This tool can also add solvent water molecules and Na+ or Cl- ions to the system. Using lammps2pdb.pl you can convert LAMMPS atom dumps into PDB files.

See the README file in the ch2lmp sub-directory for more information.

These tools were created by Pieter in’t Veld (pjintve at sandia.gov) and Paul Crozier (pscrozi at sandia.gov) at Sandia.

CMAP support added and tested by Xiaohu Hu (hux2 at ornl.gov) and Robert A. Latour (latourr at clemson.edu), David Hyde-Volpe, and Tigran Abramyan, (Clemson University) and Chris Lorenz (chris.lorenz at kcl.ac.uk), King’s College London.

10.4.4. chain tool

The file chain.f creates a LAMMPS data file containing bead-spring polymer chains and/or monomer solvent atoms. It uses a text file containing chain definition parameters as an input. The created chains and solvent atoms can strongly overlap, so LAMMPS needs to run the system initially with a “soft” pair potential to un-overlap it. The syntax for running the tool is

chain < def.chain > data.file

See the def.chain or def.chain.ab files in the tools directory for examples of definition files. This tool was used to create the system for the chain benchmark.

10.4.5. CMake tools

The cmbuild script is a wrapper around using cmake --build <dir> --target and allows compiling LAMMPS in a CMake build folder with a make-like syntax regardless of the actual build tool and the specific name of the program used (e.g. ninja-v1.10 or gmake) when using -D CMAKE_MAKE_PROGRAM=<name>.

Usage: cmbuild [-v] [-h] [-C <dir>] [-j <num>] [<target>]

  -h                print this message
  -j <NUM>          allow processing of NUM concurrent tasks
  -C DIRECTORY      execute build in folder DIRECTORY
  -v                produce verbose output

10.4.6. colvars tools

The colvars directory contains a collection of tools for post-processing data produced by the colvars collective variable library. To compile the tools, edit the makefile for your system and run “make”.

Please report problems and issues the colvars library and its tools at: https://github.com/colvars/colvars/issues


MC-based integration of multidimensional free energy gradient Version 20110511

./abf_integrate < filename > [-n < nsteps >] [-t < temp >] [-m [0|1] (metadynamics)] [-h < hill_height >] [-f < variable_hill_factor >]

The LAMMPS interface to the colvars collective variable library, as well as these tools, were created by Axel Kohlmeyer (akohlmey at gmail.com) while at ICTP, Italy.

10.4.7. createatoms tool

The tools/createatoms directory contains a Fortran program called createAtoms.f which can generate a variety of interesting crystal structures and geometries and output the resulting list of atom coordinates in LAMMPS or other formats.

See the included Manual.pdf for details.

The tool is authored by Xiaowang Zhou (Sandia), xzhou at sandia.gov.

10.4.8. drude tool

The tools/drude directory contains a Python script called polarizer.py which can add Drude oscillators to a LAMMPS data file in the required format.

See the header of the polarizer.py file for details.

The tool is authored by Agilio Padua and Alain Dequidt: agilio.padua at ens-lyon.fr, alain.dequidt at uca.fr

10.4.9. eam database tool

The tools/eam_database directory contains a Fortran program that will generate EAM alloy setfl potential files for any combination of 16 elements: Cu, Ag, Au, Ni, Pd, Pt, Al, Pb, Fe, Mo, Ta, W, Mg, Co, Ti, Zr. The files can then be used with the pair_style eam/alloy command.

The tool is authored by Xiaowang Zhou (Sandia), xzhou at sandia.gov, and is based on his paper:

X. W. Zhou, R. A. Johnson, and H. N. G. Wadley, Phys. Rev. B, 69, 144113 (2004).

10.4.10. eam generate tool

The tools/eam_generate directory contains several one-file C programs that convert an analytic formula into a tabulated embedded atom method (EAM) setfl potential file. The potentials they produce are in the potentials directory, and can be used with the pair_style eam/alloy command.

The source files and potentials were provided by Gerolf Ziegenhain (gerolf at ziegenhain.com).

10.4.11. eff tool

The tools/eff directory contains various scripts for generating structures and post-processing output for simulations using the electron force field (eFF).

These tools were provided by Andres Jaramillo-Botero at CalTech (ajaramil at wag.caltech.edu).

10.4.12. emacs tool

The tools/emacs directory contains an Emacs Lisp add-on file for GNU Emacs that enables a lammps-mode for editing input scripts when using GNU Emacs, with various highlighting options set up.

These tools were provided by Aidan Thompson at Sandia (athomps at sandia.gov).

10.4.13. fep tool

The tools/fep directory contains Python scripts useful for post-processing results from performing free-energy perturbation simulations using the USER-FEP package.

The scripts were contributed by Agilio Padua (ENS de Lyon), agilio.padua at ens-lyon.fr.

See README file in the tools/fep directory.

10.4.14. i-pi tool

The tools/i-pi directory contains a version of the i-PI package, with all the LAMMPS-unrelated files removed. It is provided so that it can be used with the fix ipi command to perform path-integral molecular dynamics (PIMD).

The i-PI package was created and is maintained by Michele Ceriotti, michele.ceriotti at gmail.com, to interface to a variety of molecular dynamics codes.

See the tools/i-pi/manual.pdf file for an overview of i-PI, and the fix ipi doc page for further details on running PIMD calculations with LAMMPS.

10.4.15. ipp tool

The tools/ipp directory contains a Perl script ipp which can be used to facilitate the creation of a complicated file (say, a lammps input script or tools/createatoms input file) using a template file.

ipp was created and is maintained by Reese Jones (Sandia), rjones at sandia.gov.

See two examples in the tools/ipp directory. One of them is for the tools/createatoms tool’s input file.

10.4.16. kate tool

The file in the tools/kate directory is an add-on to the Kate editor in the KDE suite that allow syntax highlighting of LAMMPS input scripts. See the README.txt file for details.

The file was provided by Alessandro Luigi Sellerio (alessandro.sellerio at ieni.cnr.it).

10.4.17. LAMMPS shell

New in version 9Oct2020.


The LAMMPS Shell, lammps-shell is a program that functions very similar to the regular LAMMPS executable but has several modifications and additions that make it more powerful for interactive sessions, i.e. where you type LAMMPS commands from the prompt instead of reading them from a file.

  • It uses the readline and history libraries to provide command line editing and context aware TAB-expansion (details on that below).

  • When processing an input file with the ‘-in’ or ‘-i’ flag from the command line, it does not exit at the end of that input file but stops at a prompt, so that additional commands can be issued

  • Errors will not abort the shell but return to the prompt.

  • It has additional commands aimed at interactive use (details below).

  • Interrupting a calculation with CTRL-C will not terminate the session but rather enforce a timeout to cleanly stop an ongoing run (more info on timeouts is in the timer command documentation).

These enhancements make the LAMMPS shell an attractive choice for interactive LAMMPS sessions in graphical desktop environments (e.g. Gnome, KDE, Cinnamon, XFCE, Windows).


When writing commands interactively at the shell prompt, you can hit the TAB key at any time to try and complete the text. This completion is context aware and will expand any first word only to commands available in that executable.

  • For style commands it will expand to available styles of the corresponding category (e.g. pair styles after a pair_style command).

  • For compute, fix, or dump it will also expand only to already defined groups for the group-ID keyword.

  • For commands like compute_modify, fix_modify, or dump_modify it will expand to known compute/fix/dump IDs only.

  • When typing references to computes, fixes, or variables with a “c_”, “f_”, or “v_” prefix, respectively, then the expansion will be to known compute/fix IDs and variable names. Variable name expansion is also available for the ${name} variable syntax.

  • In all other cases TAB expansion will complete to names of files and directories.

Command line editing and history

When typing commands, command line editing similar to what BASH provides is available. Thus it is possible to move around the currently line and perform various cut and insert and edit operations. Previous commands can be retrieved by scrolling up (and down) or searching (e.g. with CTRL-r).

Also history expansion through using the exclamation mark ‘!’ can be performed. Examples: ‘!!’ will be replaced with the previous command, ‘!-2’ will repeat the command before that, ‘!30’ will be replaced with event number 30 in the command history list, and ‘!run’ with the last command line that started with “run”. Adding a “:p” to such a history expansion will result that the expansion is printed and added to the history list, but NOT executed. On exit the LAMMPS shell will write the history list to a file “.lammps_history” in the current working directory. If such a file exists when the LAMMPS shell is launched it will be read to populate the history list.

This is realized via the readline library and can thus be customized with an .inputrc file in the home directory. For application specific customization, the LAMMPS shell uses the name “lammps-shell”. For more information about using and customizing an application using readline, please see the available documentation at: http://www.gnu.org/s/readline/#Documentation

Additional commands

The following commands are added to the LAMMPS shell on top of the regular LAMMPS commands:

help (or ?)    print a brief help message
history        display the current command history list
clear_history  wipe out the current command history list
save_history <range> <file>
               write commands from the history to file.
               The range is given as <from>-<to>, where <from> and <to>
               may be empty. Example: save_history 100- in.recent
source <file>  read commands from file (same as "include")
pwd            print current working directory
cd <directory> change current working directory (same as pwd if no directory)
mem            print current and maximum memory usage
|<command>     execute <command> as a shell command and return to the command prompt
exit           exit the LAMMPS shell cleanly (unlike the "quit" command)

Please note that some known shell operations are implemented in the LAMMPS shell command in a platform neutral fashion, while using the ‘|’ character will always pass the following text to the operating system’s shell command.


Compilation of the LAMMPS shell can be enabled by setting the CMake variable BUILD_LAMMPS_SHELL to “on” or using the makefile in the tools/lammps-shell folder to compile after building LAMMPS using the conventional make procedure. The makefile will likely need customization depending on the features and settings used for compiling LAMMPS.


The LAMMPS shell was not designed for use with MPI parallelization via mpirun or mpiexec or srun.

Readline customization

The behavior of the readline functionality can be customized in the ${HOME}/.inputrc file. This can be used to alter the default settings or change the key-bindings. The LAMMPS Shell sets the application name lammps-shell, so settings can be either applied globally or only for the LAMMPS shell by bracketing them between $if lammps-shell and $endif like in the following example:

$if lammps-shell
# disable "beep" or "screen flash"
set bell-style none
# bind the "Insert" key to toggle overwrite mode
"\e[2~": overwrite-mode

More details about this are in the readline documentation.

LAMMPS Shell tips and tricks

Below are some suggestions for how to use and customize the LAMMPS shell.

Enable tilde expansion

Adding set expand-tilde on to ${HOME}/.inputrc is recommended as this will change the filename expansion behavior to replace any text starting with “~” by the full path to the corresponding user’s home directory. While the expansion of filenames will happen on all arguments where the context is not known (e.g. ~/compile/lamm<TAB> will expand to ~/compile/lammps/), it will not replace the tilde by default. But since LAMMPS does not do tilde expansion itself (unlike a shell), this will result in errors. Instead the tilde-expression should be expanded into a valid path, where the plain “~/” stands for the current user’s home directory and “~someuser/” stands for “/home/someuser” or whatever the full path to that user’s home directory is.

File extension association

Since the LAMMPS shell (unlike the regular LAMMPS executable) does not exit when an input file is passed on the command line with the “-in” or “-i” flag (the behavior is like for python -i <filename>), it makes the LAMMPS shell suitable for associating it with input files based on their filename extension (e.g. “.lmp”). Since lammps-shell is a console application, you have to run it inside a terminal program with a command line like this:

xterm -title "LAMMPS Shell" -e /path/to/lammps-shell -i in.file.lmp
Use history to create an input file

When experimenting with commands to interactively to figure out a suitable choice of settings or simply the correct syntax, you may want to record part of your commands to a file for later use. This can be done with the save_history commands, which allows to selectively write a section of the command history to a file (Example: save_history 25-30 in.run). This file can be further edited (Example: |vim in.run) and then the file read back in and tried out (Example: source in.run). If the input also creates a system box, you first need to use the clear command command.

10.4.18. lmp2arc tool

The lmp2arc sub-directory contains a tool for converting LAMMPS output files to the format for Accelrys’ Insight MD code (formerly MSI/Biosym and its Discover MD code). See the README file for more information.

This tool was written by John Carpenter (Cray), Michael Peachey (Cray), and Steve Lustig (Dupont). John is now at the Mayo Clinic (jec at mayo.edu), but still fields questions about the tool.

This tool was updated for the current LAMMPS C++ version by Jeff Greathouse at Sandia (jagreat at sandia.gov).

10.4.19. lmp2cfg tool

The lmp2cfg sub-directory contains a tool for converting LAMMPS output files into a series of *.cfg files which can be read into the AtomEye visualizer. See the README file for more information.

This tool was written by Ara Kooser at Sandia (askoose at sandia.gov).

10.4.20. Magic patterns for the “file” command

New in version 10Mar2021.

The file magic contains patterns that are used by the file program available on most Unix-like operating systems which enables it to detect various LAMMPS files and print some useful information about them. To enable these patterns, append or copy the contents of the file to either the file .magic in your home directory or (as administrator) to /etc/magic (for a system-wide installation). Afterwards the file command should be able to detect most LAMMPS restarts, dump, data and log files. Examples:

$ file *.*
dihedral-quadratic.restart:   LAMMPS binary restart file (rev 2), Version 10 Mar 2021, Little Endian
mol-pair-wf_cut.restart:      LAMMPS binary restart file (rev 2), Version 24 Dec 2020, Little Endian
atom.bin:                     LAMMPS atom style binary dump (rev 2), Little Endian, First time step: 445570
custom.bin:                   LAMMPS custom style binary dump (rev 2), Little Endian, First time step: 100
bn1.lammpstrj:                LAMMPS text mode dump, First time step: 5000
data.fourmol:                 LAMMPS data file written by LAMMPS
pnc.data:                     LAMMPS data file written by msi2lmp
data.spce:                    LAMMPS data file written by TopoTools
B.data:                       LAMMPS data file written by OVITO
log.lammps:                   LAMMPS log file written by version 10 Feb 2021

10.4.21. matlab tool

The matlab sub-directory contains several MATLAB scripts for post-processing LAMMPS output. The scripts include readers for log and dump files, a reader for EAM potential files, and a converter that reads LAMMPS dump files and produces CFG files that can be visualized with the AtomEye visualizer.

See the README.pdf file for more information.

These scripts were written by Arun Subramaniyan at Purdue Univ (asubrama at purdue.edu).

10.4.22. micelle2d tool

The file micelle2d.f creates a LAMMPS data file containing short lipid chains in a monomer solution. It uses a text file containing lipid definition parameters as an input. The created molecules and solvent atoms can strongly overlap, so LAMMPS needs to run the system initially with a “soft” pair potential to un-overlap it. The syntax for running the tool is

micelle2d < def.micelle2d > data.file

See the def.micelle2d file in the tools directory for an example of a definition file. This tool was used to create the system for the micelle example.

10.4.23. moltemplate tool

The moltemplate sub-directory contains instructions for installing moltemplate, a Python-based tool for building molecular systems based on a text-file description, and creating LAMMPS data files that encode their molecular topology as lists of bonds, angles, dihedrals, etc. See the README.txt file for more information.

This tool was written by Andrew Jewett (jewett.aij at gmail.com), who supports it. It has its own WWW page at https://moltemplate.org. The latest sources can be found on its GitHub page

10.4.24. msi2lmp tool

The msi2lmp sub-directory contains a tool for creating LAMMPS template input and data files from BIOVIA’s Materias Studio files (formerly Accelrys’ Insight MD code, formerly MSI/Biosym and its Discover MD code).

This tool was written by John Carpenter (Cray), Michael Peachey (Cray), and Steve Lustig (Dupont). Several people contributed changes to remove bugs and adapt its output to changes in LAMMPS.

This tool has several known limitations and is no longer under active development, so there are no changes except for the occasional bug fix.

See the README file in the tools/msi2lmp folder for more information.

10.4.25. Scripts for building LAMMPS when offline

In some situations it might be necessary to build LAMMPS on a system without direct internet access. The scripts in tools/offline folder allow you to pre-load external dependencies for both the documentation build and for building LAMMPS with CMake.

It does so by

  1. downloading necessary pip packages,

  2. cloning git repositories

  3. downloading tarballs

to a designated cache folder.

As of April 2021, all of these downloads make up around 600MB. By default, the offline scripts will download everything into the $HOME/.cache/lammps folder, but this can be changed by setting the LAMMPS_CACHING_DIR environment variable.

Once the caches have been initialized, they can be used for building the LAMMPS documentation or compiling LAMMPS using CMake on an offline system.

The use_caches.sh script must be sourced into the current shell to initialize the offline build environment. Note that it must use the same LAMMPS_CACHING_DIR. This script does the following:

  1. Set up environment variables that modify the behavior of both, pip and git

  2. Start a simple local HTTP server using Python to host files for CMake

Afterwards, it will print out instruction on how to modify the CMake command line to make sure it uses the local HTTP server.

To undo the environment changes and shutdown the local HTTP server, run the deactivate_caches command.


For all of the examples below, you first need to create the cache, which requires an internet connection.


Afterwards, you can disconnect or copy the contents of the LAMMPS_CACHING_DIR folder to an offline system.

Documentation Build

The documentation build will create a new virtual environment that typically first installs dependencies from pip. With the offline environment loaded, these installations will instead grab the necessary packages from your local cache.

# if LAMMPS_CACHING_DIR is different from default, make sure to set it first
# export LAMMPS_CACHING_DIR=path/to/folder
source tools/offline/use_caches.sh
cd doc/
make html


CMake Build

When compiling certain packages with external dependencies, the CMake build system will download necessary files or sources from the web. For more flexibility the CMake configuration allows users to specify the URL of each of these dependencies. What the init_caches.sh script does is create a CMake “preset” file, which sets the URLs for all of the known dependencies and redirects the download to the local cache.

# if LAMMPS_CACHING_DIR is different from default, make sure to set it first
# export LAMMPS_CACHING_DIR=path/to/folder
source tools/offline/use_caches.sh

mkdir build
cd build
cmake -D LAMMPS_DOWNLOADS_URL=${HTTP_CACHE_URL} -C "${LAMMPS_HTTP_CACHE_CONFIG}" -C ../cmake/presets/most.cmake ../cmake
make -j 8


10.4.26. phonon tool

The phonon sub-directory contains a post-processing tool useful for analyzing the output of the fix phonon command in the USER-PHONON package.

See the README file for instruction on building the tool and what library it needs. And see the examples/USER/phonon directory for example problems that can be post-processed with this tool.

This tool was written by Ling-Ti Kong at Shanghai Jiao Tong University.

10.4.27. polybond tool

The polybond sub-directory contains a Python-based tool useful for performing “programmable polymer bonding”. The Python file lmpsdata.py provides a “Lmpsdata” class with various methods which can be invoked by a user-written Python script to create data files with complex bonding topologies.

See the Manual.pdf for details and example scripts.

This tool was written by Zachary Kraus at Georgia Tech.

10.4.28. pymol_asphere tool

The pymol_asphere sub-directory contains a tool for converting a LAMMPS dump file that contains orientation info for ellipsoidal particles into an input file for the PyMol visualization package or its open source variant.

Specifically, the tool triangulates the ellipsoids so they can be viewed as true ellipsoidal particles within PyMol. See the README and examples directory within pymol_asphere for more information.

This tool was written by Mike Brown at Sandia.

10.4.29. python tool

The python sub-directory contains several Python scripts that perform common LAMMPS post-processing tasks, such as:

  • extract thermodynamic info from a log file as columns of numbers

  • plot two columns of thermodynamic info from a log file using GnuPlot

  • sort the snapshots in a dump file by atom ID

  • convert multiple NEB dump files into one dump file for viz

  • convert dump files into XYZ, CFG, or PDB format for viz by other packages

These are simple scripts built on Pizza.py modules. See the README for more info on Pizza.py and how to use these scripts.

10.4.30. replica tool

The tools/replica directory contains the reorder_remd_traj python script which can be used to reorder the replica trajectories (resulting from the use of the temper command) according to temperature. This will produce discontinuous trajectories with all frames at the same temperature in each trajectory. Additional options can be used to calculate the canonical configurational log-weight for each frame at each temperature using the pymbar package. See the README.md file for further details. Try out the peptide example provided.

This tool was written by (and is maintained by) Tanmoy Sanyal, while at the Shell lab at UC Santa Barbara. (tanmoy dot 7989 at gmail.com)

10.4.31. reax tool

The reax sub-directory contains stand-alone codes that can post-process the output of the fix reax/c/bonds command from a LAMMPS simulation using ReaxFF. See the README.txt file for more info.

These tools were written by Aidan Thompson at Sandia.

10.4.32. smd tool

The smd sub-directory contains a C++ file dump2vtk_tris.cpp and Makefile which can be compiled and used to convert triangle output files created by the Smooth-Mach Dynamics (USER-SMD) package into a VTK-compatible unstructured grid file. It could then be read in and visualized by VTK.

See the header of dump2vtk.cpp for more details.

This tool was written by the USER-SMD package author, Georg Ganzenmuller at the Fraunhofer-Institute for High-Speed Dynamics, Ernst Mach Institute in Germany (georg.ganzenmueller at emi.fhg.de).

10.4.33. spin tool

The spin sub-directory contains a C file interpolate.c which can be compiled and used to perform a cubic polynomial interpolation of the MEP following a GNEB calculation.

See the README file in tools/spin/interpolate_gneb for more details.

This tool was written by the SPIN package author, Julien Tranchida at Sandia National Labs (jtranch at sandia.gov, and by Aleksei Ivanov, at University of Iceland (ali5 at hi.is).

10.4.34. singularity tool

The singularity sub-directory contains container definitions files that can be used to build container images for building and testing LAMMPS on specific OS variants using the Singularity container software. Contributions for additional variants are welcome. For more details please see the README.md file in that folder.

10.4.35. SWIG interface

The SWIG tool offers a mostly automated way to incorporate compiled code modules into scripting languages. It processes the function prototypes in C and generates wrappers for a wide variety of scripting languages from it. Thus it can also be applied to the C language library interface of LAMMPS so that build a wrapper that allows to call LAMMPS from programming languages like: C#/Mono, Lua, Java, JavaScript, Perl, Python, R, Ruby, Tcl, and more.

What is included

We provide here an “interface file”, lammps.i, that has the content of the library.h file adapted so SWIG can process it. That will create wrappers for all the functions that are present in the LAMMPS C library interface. Please note that not all kinds of C functions can be automatically translated, so you would have to add custom functions to be able to utilize those where the automatic translation does not work. A few functions for converting pointers and accessing arrays are predefined. We provide the file here on an “as is” basis to help people getting started, but not as a fully tested and supported feature of the LAMMPS distribution. Any contributions to complete this are, of course, welcome. Please also note, that for the case of creating a Python wrapper, a fully supported Ctypes based lammps module already exists. That module is designed to be object oriented while SWIG will generate a 1:1 translation of the functions in the interface file.

Building the wrapper

When using CMake, the build steps for building a wrapper module are integrated for the languages: Java, Lua, Perl5, Python, Ruby, and Tcl. These require that the LAMMPS library is build as a shared library and all necessary development headers and libraries are present.

-D WITH_SWIG=on         # to enable building any SWIG wrapper
-D BUILD_SWIG_JAVA=on   # to enable building the Java wrapper
-D BUILD_SWIG_LUA=on    # to enable building the Lua wrapper
-D BUILD_SWIG_PERL5=on  # to enable building the Perl 5.x wrapper
-D BUILD_SWIG_PYTHON=on # to enable building the Python wrapper
-D BUILD_SWIG_RUBY=on   # to enable building the Ruby wrapper
-D BUILD_SWIG_TCL=on    # to enable building the Tcl wrapper

Manual building allows a little more flexibility. E.g. one can choose the name of the module and build and use a dynamically loaded object for Tcl with:

$ swig -tcl -module tcllammps lammps.i
$ gcc -fPIC -shared $(pkgconf --cflags tcl) -o tcllammps.so \
            lammps_wrap.c -L ../src/ -llammps
$ tclsh

Or one can build an extended Tcl shell command with the wrapped functions included with:

$ swig -tcl -module tcllmps lammps_shell.i
$ gcc -o tcllmpsh lammps_wrap.c -Xlinker -export-dynamic \
         -DHAVE_CONFIG_H $(pkgconf --cflags tcl) \
         $(pkgconf --libs tcl) -L ../src -llammps

In both cases it is assumed that the LAMMPS library was compiled as a shared library in the src folder. Otherwise the last part of the commands needs to be adjusted.

Utility functions

Definitions for several utility functions required to manage and access data passed or returned as pointers are included in the lammps.i file. So most of the functionality of the library interface should be accessible. What works and what does not depends a bit on the individual language for which the wrappers are built and how well SWIG supports those. The SWIG documentation has very detailed instructions and recommendations.

Usage examples

The tools/swig folder has multiple shell scripts, run_<name>_example.sh that will create a small example script and demonstrate how to load the wrapper and run LAMMPS through it in the corresponding programming language.

For illustration purposes below is a part of the Tcl example script.

% load ./tcllammps.so
% set lmp [lammps_open_no_mpi 0 NULL NULL]
% lammps_command $lmp "units real"
% lammps_command $lmp "lattice fcc 2.5"
% lammps_command $lmp "region box block -5 5 -5 5 -5 5"
% lammps_command $lmp "create_box 1 box"
% lammps_command $lmp "create_atoms 1 box"
% set dt [doublep_value [voidp_to_doublep [lammps_extract_global $lmp dt]]]
% puts "LAMMPS version $ver"
% puts [format "Number of created atoms: %g" [lammps_get_natoms $lmp]]
% puts "Current size of timestep: $dt"
% puts "LAMMPS version: [lammps_version $lmp]"
% lammps_close $lmp

10.4.36. vim tool

The files in the tools/vim directory are add-ons to the VIM editor that allow easier editing of LAMMPS input scripts. See the README.txt file for details.

These files were provided by Gerolf Ziegenhain (gerolf at ziegenhain.com)

10.4.37. xmgrace tool

The files in the tools/xmgrace directory can be used to plot the thermodynamic data in LAMMPS log files via the xmgrace plotting package. There are several tools in the directory that can be used in post-processing mode. The lammpsplot.cpp file can be compiled and used to create plots from the current state of a running LAMMPS simulation.

See the README file for details.

These files were provided by Vikas Varshney (vv0210 at gmail.com)