[QE-users] Doubt in ecutrho behavior

[Lucas Nicolás Lodeiro Moraga]

Hello,

I have a doubt in the ecutrho behavior. I know that is not a variational
behavior with respect to energy, because the variational principle applies
to SCF step with the basis function (ecutwfc). But, I have observed that
the greater the ecutrho, the greater is the energy in some cases, like as
an anti-variational behavior (upper bound)... in other cases, the energy
oscillate without clear behavior, but converging, when increase the
ecutrho...

Why is this behavior? There are some subject with the DFT functional
description of the energy? There are some implication with the maximum
oscillation frecuency of the plane wave in the calculation of the first
derivative of the density?

Regards - Lucas
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