Total energy and energy cut-off

[ams_nanolab]

Is there any correlation between total energy of a system and the energy cutoff used in the simulations. Say I want to calculate the total energy of a large (50-60 atoms) supercell would there be any difference if I use a cutoff of 300eV in one case and 600eV in other for my LDA-PZ calculations?

[Ulrik G. Vej-Hansen]

Just to be sure, you are referring to the density mesh cutoff, right?

The short answer is yes, there is a correlation, though if 300 eV is converged, then the difference to 600 eV should be insignificant. However, note that the default unit is Hartree, not eV. Those values are fairly low for DFT, where the default value is 75 Hartree.

[ams_nanolab]

By converged you mean the error is reduced below a certain minimum tolerance value right? Or something else?

[Ulrik G. Vej-Hansen]

Yes, that is exactly what I mean