These sections provide an overview of what LAMMPS can and can't do, describe what it means for LAMMPS to be an open-source code, and acknowledge the funding and people who have contributed to LAMMPS over the years.
1.1 What is LAMMPSLAMMPS is a classical molecular dynamics code that models an ensemble of particles in a liquid, solid, or gaseous state. It can model atomic, polymeric, biological, metallic, or granular systems using a variety of force fields and boundary conditions.
For examples of LAMMPS simulations, see the Publications page of the LAMMPS WWW Site.
LAMMPS runs efficiently on single-processor desktop or laptop machines, but is designed for parallel computers. It will run on any parallel machine that compiles C++ and supports the MPI message-passing library. This includes distributed- or shared-memory parallel machines and Beowulf-style clusters.
LAMMPS can model systems with only a few particles up to millions or billions. See this section for information on LAMMPS performance and scalability, or the Benchmarks section of the LAMMPS WWW Site.
LAMMPS is a freely-available open-source code, distributed under the terms of the GNU Public License, which means you can use or modify the code however you wish. See this section for a brief discussion of the open-source philosophy.
LAMMPS is designed to be easy to modify or extend with new capabilities, such as new force fields, atom types, boundary conditions, or diagnostics. See this section for more details.
The current version of LAMMPS is written in C++. Earlier versions were written in F77 and F90. See this section for more information on different versions. All versions can be downloaded from the LAMMPS WWW Site.
LAMMPS was originally developed under a US Department of Energy CRADA (Cooperative Research and Development Agreement) between two DOE labs and 3 companies. It is distributed by Sandia National Labs. See this section for more information on LAMMPS funding and individuals who have contributed to LAMMPS.
In the most general sense, LAMMPS integrates Newton's equations of motion for collections of atoms, molecules, or macroscopic particles that interact via short- or long-range forces with a variety of initial and/or boundary conditions. For computational efficiency LAMMPS uses neighbor lists to keep track of nearby particles. The lists are optimized for systems with particles that are repulsive at short distances, so that the local density of particles never becomes too large. On parallel machines, LAMMPS uses spatial-decomposition techniques to partition the simulation domain into small 3d sub-domains, one of which is assigned to each processor. Processors communicate and store "ghost" atom information for atoms that border their sub-domain. LAMMPS is most efficient (in a parallel sense) for systems whose particles fill a 3d rectangular box with roughly uniform density. Papers with technical details of the algorithms used in LAMMPS are listed in this section.
This section highlights LAMMPS features, with pointers to specific commands which give more details. If LAMMPS doesn't have your favorite interatomic potential, boundary condition, or atom type, see this section, which describes how you can add it to LAMMPS.
(atom style command)
(pair style, bond style, angle style, dihedral style, improper style, kspace style commands)
(read_data, lattice, create_atoms, delete_atoms, displace_atoms comands)
(fix command)
(run, run_style, temper commands)
LAMMPS is designed to efficiently compute Newton's equations of motion for a system of interacting particles. Many of the tools needed to pre- and post-process the data for such simulations are not included in the LAMMPS kernel for several reasons:
Specifically, LAMMPS does not:
A few tools for pre- and post-processing tasks are provided as part of the LAMMPS package; they are described in this section. However, many people use other codes or write their own tools for these tasks.
LAMMPS requires as input a list of initial atom coordinates and types, molecular topology information, and force-field coefficients assigned to all atoms and bonds. LAMMPS will not build molecular systems and assign force-field parameters for you.
For atomic systems LAMMPS provides a create_atoms command which places atoms on solid-state lattices (fcc, bcc, etc). Assigning small numbers of force field coefficients can be done via the pair coeff, bond coeff, angle coeff, etc commands. For molecular systems or more complicated simulation geometries, users typically use another code as a builder and convert its output to LAMMPS input format, or write their own code to generate atom coordinate and molecular topology for LAMMPS to read in.
For complicated molecular systems (e.g. a protein), a multitude of topology information and hundreds of force-field coefficients must typically be specified. We suggest you use a program like CHARMM or AMBER or other molecular builders to setup such problems and dump its information to a file. You can then reformat the file as LAMMPS input. Some of the tools in this section can assist in this process.
Similarly, LAMMPS creates output files in a simple format. Most users post-process these files with their own analysis tools or re-format them for input into other programs, including visualization packages. If you are convinced you need to compute something on-the-fly as LAMMPS runs, see this section for a discussion of how you can use the dump and fix commands to print out data of your choosing. Keep in mind that complicated computations can slow down the molecular dynamics timestepping, particularly if the computations are not parallel, so it is often better to leave such analysis to post-processing codes.
A very simple (yet fast) visualizer is provided with the LAMMPS package - see the xmovie tool in this section. It creates xyz projection views of atomic coordinates and animates them. We find it very useful for debugging purposes. For high-quality visualization we recommend the following packages:
Other features that LAMMPS does not yet (and may never) support are discussed in this section.
Finally, these are freely-available molecular dynamics codes, most of them parallel, which may be well-suited to the problems you want to model. They can also be used in conjunction with LAMMPS to perform complementary modeling tasks.
CHARMM, AMBER, NAMD, NWCHEM, and Tinker are designed primarily for modeling biological molecules. CHARMM and AMBER use atom-decomposition (replicated-data) strategies for parallelism; NAMD and NWCHEM use spatial-decomposition approaches, similar to LAMMPS. Tinker is a serial code. DL_POLY includes potentials for a variety of biological and non-biological materials; both a replicated-data and spatial-decomposition version exist.
LAMMPS comes with no warranty of any kind. As each source file states in its header, it is a copyrighted code that is distributed free-of- charge, under the terms of the GNU Public License (GPL). This is often referred to as open-source distribution - see www.gnu.org or www.opensource.org for more details. The legal text of the GPL is in the LICENSE file that is included in the LAMMPS distribution.
Here is a summary of what the GPL means for LAMMPS users:
(1) Anyone is free to use, modify, or extend LAMMPS in any way they choose, including for commercial purposes.
(2) If you distribute a modified version of LAMMPS, it must remain open-source, meaning you distribute it under the terms of the GPL. You should clearly annotate such a code as a derivative version of LAMMPS.
(3) If you release any code that includes LAMMPS source code, then it must also be open-sourced, meaning you distribute it under the terms of the GPL.
(4) If you give LAMMPS files to someone else, the GPL LICENSE file and source file headers (including the copyright and GPL notices) should remain part of the code.
In the spirit of an open-source code, these are various ways you can contribute to making LAMMPS better. You can send email on any of these items.
LAMMPS development has been funded by the US Department of Energy (DOE), through its CRADA, LDRD, ASCI, and Genomes-to-Life programs and its OASCR and OBER offices.
Specifically, work on the latest version was funded in part by the US Department of Energy's Genomics:GTL program (www.doegenomestolife.org) under the project, "Carbon Sequestration in Synechococcus Sp.: From Molecular Machines to Hierarchical Modeling".
The following papers describe the parallel algorithms used in LAMMPS.
S. J. Plimpton, Fast Parallel Algorithms for Short-Range Molecular Dynamics, J Comp Phys, 117, 1-19 (1995).
S. J. Plimpton, R. Pollock, M. Stevens, Particle-Mesh Ewald and rRESPA for Parallel Molecular Dynamics Simulations, in Proc of the Eighth SIAM Conference on Parallel Processing for Scientific Computing, Minneapolis, MN (March 1997).
If you use LAMMPS results in your published work, please cite the J Comp Phys reference and include a pointer to the LAMMPS WWW Site (www.cs.sandia.gov/~sjplimp/lammps.html). A paper describing the latest version of LAMMPS is in the works; when it appears in print, you can check the LAMMPS WWW Site for a more current citation.
If you send me information about your publication, I'll be pleased to add it to the Publications page of the LAMMPS WWW Site. Ditto for a picture or movie for the Pictures or Movies pages.
The primary author of LAMMPS is Steve Plimpton at Sandia National Labs. Others have made significant contributions to the code:
Ewald and PPPM solvers | Roy Pollock (LLNL) |
rRESPA | Mark Stevens & Paul Crozier (Sandia) |
NVT/NPT integrators | Mark Stevens (Sandia) |
class 2 force fields | Eric Simon (Cray) |
HTFN energy minimizer | Todd Plantenga (Sandia) |
msi2lmp tool | Steve Lustig (Dupont), Mike Peachey & John Carpenter (Cray) |
CHARMM force fields | Paul Crozier (Sandia) |
2d Ewald/PPPM | Paul Crozier (Sandia) |
granular force fields and BC | Leo Silbert & Gary Grest (Sandia) |
multi-harmonic dihedral potential | Mathias Putz (Sandia) |
EAM potentials | Stephen Foiles (Sandia) |
parallel tempering | Mark Sears (Sandia) |
lmp2cfg and lmp2traj tools | Ara Kooser, Jeff Greathouse, Andrey Kalinichev (Sandia) |
FFT support for SGI SCLS (Altix) | Jim Shepherd (Ga Tech) |
targeted molecular dynamics (TMD) | Paul Crozier (Sandia), Christian Burisch (Bochum Univeristy, Germany) |
force tables for long-range Coulombics | Paul Crozier (Sandia) |
radial distribution functions | Paul Crozier (Sandia) |
Morse bond potential | Jeff Greathouse (Sandia) |
charmm2lmp tool | Pieter in't Veld and Paul Crozier (Sandia) |
Other CRADA partners involved in the design and testing of LAMMPS were