This is the home page for the classical molecular dynamics code LAMMPS, which stands for Large-scale Atomic/Molecular Massively Parallel Simulator. The current version of LAMMPS is 22 Jan 2008.

LAMMPS has potentials for soft materials (biomolecules, polymers) and solid-state materials (metals, semiconductors) and coarse-grained systems. It can be used to model atoms or, more generically, as a parallel particle simulator at the mesoscale or continuum levels.

LAMMPS runs on single processors or in parallel using message-passing techniques and a spatial-decomposition of the simulation domain. The code is designed to be easy to modify or extend with new functionality.

LAMMPS is distributed as an open source code under the terms of the GPL. The current version can be downloaded here. This includes links to the last major release, the latest upgraded version with all subsequent bug fixes and new features, and older F90/F77 versions. The last major release is also available on SourceForge.

LAMMPS is distributed by Sandia National Laboratories, a US Department of Energy laboratory. The main authors of LAMMPS are listed here along with other contributors. Funding for LAMMPS development has come primarily from DOE (OASCR, OBER, ASCI, LDRD, Genomes-to-Life) and is acknowledged here.

• (1/08) Release of 22 Jan 2008 version of LAMMPS. New features include revamped LAMMPS output options for thermodynamic and dump output, thermo_style custom and dump custom can now access computes, fixes, and variables directly, new enhanced versions of the fix ave/time, fix ave/spatial, and fix ave/atom commands, per-atom energy and virial tabulations for all pair and many-body potentials and fixes that invoke internal constraints, and a new easier-to-use variable formula syntax. New commands added are fix dt/reset, pair_style lubricate, pair coul/debye, fix coord/original, compute pe/atom, compute stress/atom, compute sum, pair_style resquared, fix viscosity, and compute displace/atom. Deprecated commands are "fix gran/diag", "compute epair/atom", "compute ebond/atom", "compute variable/atom", "compute variable", "compute sum/atom", and "compute attribute/atom". See details here.
• (10/07) Release of 5 Oct 2007 version of LAMMPS. New features include displace_box, change_box, compute ebond/atom, changes to 2d pressure computation, rigid bodies with fix deform, pair_style airebo, fix nve/limit, fix ave/atom, compute attribute/atom, compute sum/atom, user-contributed packages, pair_style hybrid/overlay for superposing pairwise potentials, kspace_style ewald/n for long-range dispersion contributions from 1/r^6 LJ terms, pair_style lj/coul, pair_style buck/coul, compute ackland/atom. See details here.
• (6/07) Release of 22 Jun 2007 version of LAMMPS. New features include static and dynamic non-orthogonal simulation boxes (triclinic symmetry), fix heat, if command, new Finnis/Sinclair EAM potentials, displace_atoms random, new set options, create_atoms single, compute coord/atom, fix ave/time, fix ave/spatial, variable atom, new COLLOID package with pair colloid potential and neighbor and communication options to support it, new DIPOLE package for point-dipole particles with pair dipole/cut, new ASPHERE package for ellipsoidal particles with a GayBerne potential and aspherical particle integrators to support it, NEMD simulations via fix deform and fix nvt/sllod and compute temp/deform, and tools/pymol_asphere for ellipsoidal particles. See details here.
• (3/07) LAMMPS now has support for triclinic (non-orthogonal) simulation boxes. See details here for the 7Mar07 patch. Thanks to Pieter in 't Veld (Sandia) for his efforts to help add this capability.
• (2/07) Release of 12 Feb 2007 version of LAMMPS. New features include Tersoff, Stillinger-Weber, and MEAM (modified EAM) potentials; non-orthogonal lattices; fix wall/lj126; fix deposit; uloop variables; removal of global variables so that LAMMPS can be instantiated multiple times as a library; optimized versions of lj/cut, eam, morse, and lj/charmm/coul/long pair potentials; compute command which now encompasses temperature, pressure, and per-atom calculations; new options for thermo_style custom, dump custom, and variable equal output; and higher-precision real/metal units. See details here.
• Old

This is work by A-Jing Cao (chaoajing at lnm.imech.ac.cn) and Yue-Guang Wei (ywei at lnm.imech.ac.cn) at the Laboratory of Nonlinear Mechanics (LNM), Institute of Mechanics, Chinese Academy of Sciences.

The picture on the left is the equilibrium structure of a nanowire constructed with a fivefold twinned grain boundary running down the axis of the wire. Tensile stress is applied. The picture in the middle shows the resulting dislocation pile-up. The picture on the right shows a different geometry where twin boundaries are oriented perpendicular to the axis of the nanowire. Atoms are colored according to the configuration of their neighbors; the visualization was done with the AtomEye program.

These papers have further details:

Formation of Fivefold Deformation Twins in Nanocrystalline Face-Centered-Cubic Copper Based on Molecular Dynamics Simulations, A. J. Cao and Y. G. Wei, Applied Physics Lett, 89, 041919 (2006). (abstract)

Atomistic simulations of the mechanical behavior of fivefold twinned nanowires, A. J. Cao and Y. G. Wei, Phys Rev B, 74, 214108 (2006). (abstract)

Deformation mechanisms of face-centered-cubic metal nanowires with twin boundaries, A. J. Cao, Y. G. Wei, and S. X. Mao, Applied Physics Letters, 90, 151909 (2007). (abstract)