Dear LAMMPS Users,
I noticed that in some papers and examples, they use fix npt command to set up the initial pressure of the system, and they use 0 as the initial pressure. Is there any reasons to use 0 at the beginning of the simulation? What is the effect if I set it to 1 bar during the initialization (to simulate room atmosphere at the beginning)?
Thank you,
Steven
The difference between 0 and 1 is negligible for condensed systems at typical system sizes. Your pressure fluctuations will be much larger.
Depending on how high potential energy your initial geometry has, you may want to start with fix nvt or fix nve plus fix langevin to dissipate the potential energy without your system expanding. With fix npt it can take a very long time to undo the initial expansion from a high energy system.
Dear Prof. Akohlmey,
That’s very a professional answer! Thank you so much for your help！
Sincerely,
Steven
Dear Prof. Akohlmey,
Sorry I just have another question. If we use fix npt to relax the system after initialization, the system may expand, will it also change the lattice constant of the material? I know the temperature can affect the lattice constant, but I’m confused whether pressure or volume also has big effects on lattice constant.
Thank you,
Steven
You are trying to turn me into your adviser again. I will not discuss science topics here. Talk to your adviser or somebody familiar with your research that can advise you. We’ve been over this topic already.