LAMMPS GUI is essentially a small graphical text editor that is linked to the LAMMPS library and thus can run LAMMPS using the contents of the text buffer as input. This is similar to what people usually would do using a text editor to edit the input and then a command line terminal window to run the input commands. The main benefit is that this integrates very well with graphical desktop environments and that it is easier to use for beginners in running computations and thus very suitable for tutorials on LAMMPS.

Features

The main window of the LAMMPS GUI is a text editor window with syntax highlighting set up for LAMMPS input files. It can be used to edit any kind of text file, but then trying to run those files will cause errors. The output of a run is captured and displayed in a separate window dialog. The log window is updated during the run and a progress bar for each run command shown in the main window. Starting a new run will open another log windows. After the simulation is finished, an image of the simulated system can be created and shown in another window. Ongoing runs can be stopped at the next iteration via triggering a timeout.

When opening a file, the editor will determine the directory where the file resides and switch its current working directory to that folder. Many LAMMPS inputs contain commands that read other files, typically from the folder with the input file. The GUI will show the current working directory. The editor window can also receive (entire) files via drag-n-drop from a file manager GUI or a desktop environment.

Almost all commands are accessible via hotkeys. Which those hotkeys are, is shown next to the entries in the menu. Log and image viewer windows can be closed with CTRL-W (or Command-W on macOS). The "About LAMMPS" dialog will show the LAMMPS version and the features included into the LAMMPS library linked to the LAMMPS GUI.

Due to its nature as a graphical application, it is not possible to use the LAMMPS GUI in parallel with MPI, but OpenMP multi-threading is available.

Prerequisites and portability

LAMMPS GUI is programmed using the Qt cross-platform GUI toolkit, currently using Qt version 5.15LTS for better compatibility with older compilers. It has been successfully compiled and tested on:

Fedora Linux 38 x86_64 using GCC 13 and Clang 16
Apple macOS 12 (Monterey) and macOS 13 (Ventura) with Xcode on arm64 and x86_64
Windows 10 and 11 x86_64 with Visual Studio 2022 and Visual C++ 14.36

Compilation

The source for the LAMMPS GUI is included with the LAMMPS source code distribution in the folder tools/lammps-gui and thus it can be can be built as part of a regular LAMMPS compilation. Using CMake is required. To enable its compilation the CMake variable -D BUILD_LAMMPS_GUI=on must be set when creating the CMake configuration. All other settings (compiler, flags, compile type) for LAMMPS GUI are then inherited from the regular LAMMPS build. If the Qt library is packaged for Linux distributions, then its location is typically auto-detected since the required CMake configuration files are stored in a location where CMake can find them without additional help. Otherwise, the location of the Qt library installation must be indicated by setting -D Qt5_DIR=/path/to/qt5/lib/cmake/Qt5, which is a path to a folder inside the Qt installation that contains the file Qt5Config.cmake.

It is also possible to build the LAMMPS GUI as a standalone executable (e.g. when LAMMPS has been compiled with traditional make), then the CMake configuration needs to be told where to find the LAMMPS headers and the LAMMPS library, via -D LAMMPS_SOURCE_DIR=/path/to/lammps/src. CMake will try to guess a build folder with the LAMMPS library from that path, but it can also be set with -D LAMMPS_LIB_DIR=/path/to/lammps/lib.

Rather than linking to the LAMMPS library during compilation, it is also possible to compile the GUI with a plugin loader library that will load the LAMMPS library at runtime during startup of the GUI from a shared library; e.g. liblammps.so or liblammps.dylib or liblammps.dll depending on the operating system. This has the advantage that the LAMMPS library can be updated LAMMPS without having to recompile the GUI. The ABI of the LAMMPS C-library interface is very stable and generally backward compatible. This feature is enabled by setting -D LAMMPS_GUI_USE_PLUGIN=on and then -D LAMMPS_PLUGINLIB_DIR=/path/to/lammps/plugin/loader. Typically, this would be the examples/COUPLE/plugin folder of the LAMMPS distribution.

Platform notes

macOS

When building on macOS, the build procedure will try to manufacture a drag-n-drop installer, LAMMPS-macOS-multiarch.dmg. To build multi-arch executables that will run on both, arm64 and x86_64 architectures natively, it is necessary to set the CMake variable -D CMAKE_OSX_ARCHITECTURES=arm64;x86_64. To achieve wide compatibility with different macOS versions, you can also set -D CMAKE_OSX_DEPLOYMENT_TARGET=11.0 which will set compatibility to macOS 11 (Big Sur) and later, even if you are compiling on a more recent macOS version.

updated by Axel Kohlmeyer, 08/1023