I have downloaded POSCAR file for "WS2" from "materials project website". I want to do lattice optimization, draw "Energy versus lattice parameters" curves, and calculate Bulk modulus through Birch–Murnaghan equation of state. So, could you please show how to do that, and if there is a script that I can rely on ?
This can be readily done using the Atomic Simulation Environment (ASE), if you are comfortable with Python. A tutorial for this exact purpose is described here. Another example using ASE can be found in Section 4.3 of Kitchin's "Modeling materials using density functional theory".