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Energy increased with more kpoints

PostPosted: Tue Feb 26, 2019 1:38 pm
by mdsimulationgroup
Hello,

I am attempting to look at the kpoint grid convergence but the energy increased as the grid size got bigger:

etotal1 -1.1016678839E+04
etotal2 -1.1013220577E+04
etotal3 -1.1012798679E+04
etotal4 -1.1012928525E+04

I've attached my input file.

Thanks for the help!
Stacey

Re: Energy increased with more kpoints

PostPosted: Tue Feb 26, 2019 5:01 pm
by ebousquet
Dear Stacey,
Sounds like you might still need to increase the number of k-points to get convergence.
You can check by also reporting the change of energy w.r.t. the most converged case (here 6x6x6):
Code: Select all
            ETOT, Ha            Dela-ETOT, mHa
etotal1   -1.1016678839E+04   -3750.31
etotal2   -1.1013220577E+04   -292.05
etotal3   -1.1012798679E+04   129.84
etotal4   -1.1012928525E+04   0

The difference between 6x6x6 and 4x4x4 is 129.84 mHa but is smaller than w.r.t. 2x2x2 (-292.05 mHa).
Best wishes,
Eric