Hi Connor,
Convergence means that changing some input parameter you get variation of
structure energy is in the margin set according to certain criteria. So, if
you think that energy upon variation ecutwfc from 70 to 80 changes not much
then you can consider your calculations converged.
As a rule of thumb ecutwfc equal to 70-75 is enough for normconserving
pseudopotentials and can be even less (30 40) for ultrasoft/paw ones.
Sincerely yours,
M. V. Kondrin
On Sep 24 2022, Connor Wilson wrote:
Hi everyone,
I apologize if what follows is a neophytic question. I'm currently
studying the vibrational properties of high-entropy oxides (HEOs). I've
managed to relax a 64-atom supercell of HEO such that the force acting on
each atom is less than 1E-6 Ry/au. My confusion regards the optimal
choice of ecutwfc, kpoints, etc.
I understand I should perform convergence tests with respect to the
parameters I'm interested in, and as I intend on studying the phonons, I
should think this entails converging the forces, stresses, and lattice
parameters.
Therefore: to choose the optimal ecutwfc (say), should I perform vc-relax
calculations using ecutwfc=60,70,etc, and chose the value of ecutwfc
which gives the best compromise between runtime and force, stress,
lattice parameter, etc convergence? Would this be a reasonable way of
conducting the convergence testing?
Thank you for your help,
Connor Wilson
MSc candidate in Condensed Matter Physics
Brock University
St. Catharines, ON, CAN, L2S 3A1
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