[QE-users] "Re2: Convergence Issues?"

[Stefano Baroni]

I beg to slight differ. It does not make much sense to assign a “default value” to the Gaussian smearing, unless one makes sure that the computations are well converged with respect to the number of k points, for that specific value of the smearing. The rational procedure to follow is: 1) start with whatever value of the smearing one wishes, and make sure that the (internal, *not* “fake free”) energy is well converged with respect to the number of k points. If the number of k points is sufficient, it is likely that no nasty oscillation would arise; 2) decrease the smearing and vary the number of k points accordingly. HTH — Stefano B


—
Stefano Baroni -  SISSA, Trieste - http://stefano.baroni.me, stefanobaroni (skype)

I do not mind if you think slowly, but I do object when you publish more quickly than you think [W.E. Pauli to an unknown colleague, as reported by N. Kemmer]

> On 25 Jan 2021, at 15:08, Lucas Nicolás Lodeiro Moraga <lucas.lodeiro at ug.uchile.cl> wrote:
> 
> Hi, 
> It appears a metallic oscillation, where a couple or more states change their relative energy, and change their energetical order, then the occupation changes abruptly (non continuous). If this is the problem, it is better to increase the degauss value and/or change the smearing method.
> Typically I use methfessel-paxton with 0.015 Ry for degauss, which mimics the VASP default values. When you get a converged system, you can try to decrease (slowly) the degauss.
> 
> Regards - Lucas Lodeiro
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