LAMMPS example problems

There are 3 flavors of sub-directories in this file, each with sample problems you can run with LAMMPS.

lower-case directories = simple test problems for LAMMPS and its packages upper-case directories = more complex problems USER directory with its own sub-directories = tests for USER packages

Each is discussed below.

---

Lower-case directories

Each of these sub-directories contains a sample problem you can run with LAMMPS. Most are 2d models so that they run quickly, requiring a few seconds to a few minutes to run on a desktop machine. Each problem has an input script (in.*) and produces a log file (log.*) and (optionally) a dump file (dump.*) or image files (image.*) when it runs. Some use a data file (data.*) of initial coordinates as additional input. Some require that you install one or more optional LAMMPS packages.

A few sample log file outputs on different machines and different numbers of processors are included in the directories to compare your answers to. E.g. a log file like log.crack.date.foo.P means it ran on P processors of machine "foo" with the dated version of LAMMPS. Note that these problems should get statistically similar answers when run on different machines or different numbers of processors, but not identical answers to those in the log of dump files included here. See the Errors section of the LAMMPS documentation for more discussion.

If you uncomment the dump command in the input script, a text dump file will be produced, which can be animated by various visualization programs (see http://lammps.sandia.gov/viz.html). It can also be animated using the xmovie tool described in the Additional Tools section of the LAMMPS documentation.

If you uncomment the dump image command in the input script, and assuming you have built LAMMPS with a JPG library, JPG snapshot images will be produced when the simulation runs. They can be quickly post-processed into a movie using commands described on the dump image doc page.

Animations of many of these examples can be viewed on the Movies section of the LAMMPS WWW Site.

These are the sample problems and their output in the various sub-directories:

body: body particles, 2d system colloid: big colloid particles in a small particle solvent, 2d system comb: models using the COMB potential crack: crack propagation in a 2d solid dipole: point dipolar particles, 2d system dreiding: methanol via Dreiding FF eim: NaCl using the EIM potential ellipse: ellipsoidal particles in spherical solvent, 2d system flow: Couette and Poiseuille flow in a 2d channel friction: frictional contact of spherical asperities between 2d surfaces gpu: use of the GPU package for GPU acceleration hugoniostat: Hugoniostat shock dynamics indent: spherical indenter into a 2d solid kim: use of potentials in Knowledge Base for Interatomic Models (KIM) line: line segment particles in 2d rigid bodies meam: MEAM test for SiC and shear (same as shear examples) melt: rapid melt of 3d LJ system micelle: self-assembly of small lipid-like molecules into 2d bilayers min: energy minimization of 2d LJ melt msst: MSST shock dynamics neb: nudged elastic band (NEB) calculation for barrier finding nemd: non-equilibrium MD of 2d sheared system obstacle: flow around two voids in a 2d channel peptide: dynamics of a small solvated peptide chain (5-mer) peri: Peridynamic model of cylinder impacted by indenter pour: pouring of granular particles into a 3d box, then chute flow prd: parallel replica dynamics of vacancy diffusion in bulk Si reax: RDX and TATB models using the ReaxFF rigid: rigid bodies modeled as independent or coupled shear: sideways shear applied to 2d solid, with and without a void srd: stochastic rotation dynamics (SRD) particles as solvent tad: temperature-accelerated dynamics of vacancy diffusion in bulk Si tri: triangular particles in rigid bodies

Here is how you might run and visualize one of the sample problems:

cd indent cp ../../src/lmp_linux . # copy LAMMPS executable to this dir lmp_linux < in.indent # run the problem

Running the simulation produces the files {dump.indent} and {log.lammps}. You can visualize the dump file as follows:

../../tools/xmovie/xmovie -scale dump.indent

If you uncomment the dump image line(s) in the input script a series of JPG images will be produced by the run. These can be viewed individually or turned into a movie or animated by tools like ImageMagick or QuickTime or various Windows-based tools. See the dump image doc page for more details. E.g. this Imagemagick command would create a GIF file suitable for viewing in a browser.

% convert -loop 1 *.jpg foo.gif

---

Upper-case directories

The COUPLE directory has examples of how to use LAMMPS as a library, either by itself or in tandem with another code or library. See the COUPLE/README file to get started.

The ELASTIC directory has an example script for computing elastic constants, using a zero temperature Si example. See the ELASTIC/in.elastic file for more info.

The USER directory contains subdirectories of user-provided example scripts for ser packages. See the README files in those directories for more info. See the doc/Section_start.html file for more info about installing and building user packages.