I am just starting my PhD, and my topic is “Molecular dynamics investigation of pressure-dependent interfacial rheology in a gas-saturated crude oil-brine system with eco-compatible demulsifier.” I have never used MD before now. I know the physics behind my research, but I don’t know where to begin with using MD to achieve this work. I will need all the help to get started with this work.
Since MD is the topic of your PhD, there surely must be someone in your department (ideally, one of your supervisor, advisor, or co-workers) which has this expertise. You definitely do not want to outsource this skill in a forum: no one has the time and dedication needed to provide university-grade higher education to online students.
Good luck for your research. If you have problems using LAMMPS:
read the documentation for the specific command
study the examples shipped with the source code
search the forum, there is a lot of wisdom here
last resort: post a new question when you are absolutely sure no one has asked that before.