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

2021-01-25 Thread Stephen Zhang
Thank you all for your suggestions. I think the best move would be to increase the smearing value until I achieve convergence. I also wanted to ask, but would mixing = 'local-tf' be a good mixing method for this system? The crystal has been confirmed experimentally to be a metal, and I the

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

2021-01-25 Thread Stefano Baroni
We do not necessarily disagree. The internal energy is harder to converge than the free energy, because the first is not variational, whereas the latter is so. Also, level crossing is obviously much reduced (and eventually eliminated) for large enough smearing. S. > On 25 Jan 2021, at 16:59,

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

2021-01-25 Thread Nicola Marzari
Dear Stefano, Lucas, this is one of the few areas where I disagree with Stefano - I think we should use the free energy (forces and stresses are the total derivative of the free energy, not the internal energy), and that level-crossing instabilities are exceedinfly difficult to cure with

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

2021-01-25 Thread 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

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

2021-01-25 Thread Lucas Nicolás Lodeiro Moraga
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.