What is LAMMPS?

Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) is an open-source, Molecular dynamics software, basically written on C++, finds it's application in fields like material science, molecular biology, drug discovery and many more. It works on the principle of Statistical mechanic and solves various Newtonian equations for each and every atom specified in the system.

As I am particularly working on materials, I would like to share some of the useful features of LAMMPS:

Statistical mechanics

Classical thermodynamics considers only the macroscopic properties of the system and explain the relationship between those properties. It does not explain how those properties are acquired by the system. Statistical mechanics provides a connection between microscopic and macroscopic behaviour of the system.

Prerequisites

1. Basic knowledge in material science

2. Basics of statistical mechanics

3. LAMMPS software

4. Ovito software

5. Atom text editor (You can also use Notepad instead of Atom if you are a windows user)

Input and output files

Input File

Input script of LAMMPS can be written in any text editor. I generally use the Atom text editor. You can also use Notepad. The format of the input script should be ".txt" or ".in". While writing the input script, you should keep in mind that LAMMPS read the script one line at a time. It reads a line, executes it and then it goes to the next line. So be cautious on what command should be executed first. Also, you can add comments to the script wherever you want my just adding # before the comment. Anything after a # will not be executed by LAMMPS.

Interatomic Potential

Force acting between atoms are termed as interatomic potential. It is really important to specify this force in LAMMPS script. We do that using the commands pair_style and pair_coeff. There are different types of potentials available like LJ, EAM, EAM/Alloy etc. pair_style specifies the potential type and pair_coeff specifies potential values.