How to improve the calculation speed

[hydrogen1222]

Dear developer, I installed VASP on my personal computer for my own study and use (not for academic or commercial purposes). I did not install slurm. My VASP usage is to run "vasp_std" or "mpirun -np 8" in the directory of the input file. How can I speed up the calculation in this case？
Looking for your reply, thanks!

[ftherrien]

Hi @hydrogen1222, what kind of system are you working with? DFT calculations with VASP are usually expensive and can take a lot of time on a local machine. Did you complete a single DFT calculation of your system prior to running VaspGibbs?

[hydrogen1222]

Thank your reply. My calculation system is very small, it is a conventional cell of sodium chloride crystal. I have completed structural optimization and SCF calculation

[ftherrien]

What are you wanting to use VaspGibbs for? Do you have an adsorbate on an NaCl surface?

[hydrogen1222]

What are you wanting to use VaspGibbs for? Do you have an adsorbate on an NaCl surface?

Thank you for your reply. There are no adsorbates on the surface of sodium chloride crystals, which is pure sodium chloride. I want to calculate the Gibbs free energy of sodium, chlorine, and sodium chloride separately, and then calculate the Gibbs free energy change for the formation of sodium chloride. Just out of curiosity, I am not sure if this method is reliable or absurd

[ftherrien]

I coded VaspGibbs to do adsorption energy calculations, I did not implement what is necessary to get bulk free energies (which require phonon calculations). I think you can technically get close with VaspGibbs if you create a large supercell and you are ok with assuming that the solid is incompressible, but the calculation will take a lot of time so you are probably better off with phonopy.

That being said you can find the formation energy of NaCl (the energy of NaCl with respect to Na and Cl) on the Materials Project website here. If you are just looking for an approximation this is probably what you are looking for. The formation free energy won't be very different from the formation energy around room temperature for solids with solid elementary phases. So if you already have energies for Na, Cl and NaCl you already have what you need and you should obtain about the same thing as what the MP calculated: ~2eV/atom