Hi Matthew,
I've often heard it said that 1meV/atom is a good criterion for convergence tests to set ecutwfc, ecutrho and K-point sampling. I wonder if that makes sense in if the structure has very light and heavy atoms. One I'm working on now contains Ca, Si, O and H. Since each H contributes only one electron, should it count equally in the tally of 104 atoms? Should the criterion be a certain energy/total electron? Energy/valence electron (defined in the pseudo)?
Convergence of ecutwfc/ecutrho is a property of the pseudpotential used, so you should converge ecutwfc/ecutrho for the each new atom type (pseudopotential) in your system and then used the maximum value obtained for all calculations. A hint for appropriate values is typically listed in the pseudopotential file. The easiest way to do this is just to make a small box containing the atom and increase ecutwfc (using lets say ecutrho=8*ecutwfc_max) until the energy stays within approx ~1 mRy. Once you obtain the converged ecutwfc then you can decrease ecutrho to a more appropriate value.
Here is a hands-on presentation from a workshop where this is described: http://indico.ictp.it/event/7921/session/320/contribution/1261/material/0/
Best Regards, Matic -- Matic Poberznik J. Stefan Institute, Jamova 39, Ljubljana, Slovenia _______________________________________________ Quantum ESPRESSO is supported by MaX (www.max-centre.eu/quantum-espresso) users mailing list [email protected] https://lists.quantum-espresso.org/mailman/listinfo/users
