Dump Files in LAMMPS
LAMMPS is a widely-used molecular dynamics simulation software that allows researchers to simulate the behavior of atoms and molecules in various initial conditions. During a simulation, LAMMPS generates a variety of output files, including dump files. Dump files are text files that contain information about the state of the system at a particular point in time during the simulation. They can be generated at regular intervals or triggered by specific events, such as the application of a force or the occurrence of a collision. The information contained in a dump file can be used to analyze the behavior of the system and to visualize the positions, velocities, and other properties of the atoms and molecules. The format of a dump file is determined by the user-specified dump style. LAMMPS provides several dump styles, including atom, custom, image, and trajectory. The atom style generates a simple text file that lists the position, velocity, and other properties of each atom in the system. The custom style allows users to specify which properties to include in the dump file and in what order. The image style is similar to the atom style. The trajectory style generates a file that can be read by visualization software to create an animation of the simulation. The “dump” command which used in LAMMS scripts for dump files produce depicted in below figure.
Dump files can be quite large, depending on the size of the system and the frequency at which they are generated. Technically, users can specify the filename and frequency of dump files using the dump command. For example, the command “dump 1 all atom 20000 dump.atom” would generate an atom-style dump file every 20000 timesteps and save it as “dump.atom”. Once a dump file has been generated, it can be analyzed using various tools, such as Python scripts or visualization software. For example, a Python script could be used to extract the positions of all atoms at a particular timestep and calculate the distance between them. Visualization packages such as VMD or OVITO can be used to create pictures/animations of the simulation or to visualize the positions and properties of atoms over time. Below video shows dump file production procedure in LAMMPS package.