[Wien] density matrix is not positive

[Laurence Marks]

..untested option (not unrelated)

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_____
Professor Laurence Marks
"Research is to see what everybody else has seen, and to think what nobody
else has thought", Albert Szent-Gyorgi
www.numis.northwestern.edu

On Fri, Jan 3, 2020, 06:06 Laurence Marks <laurence.marks at gmail.com> wrote:

> I am not surprised that you see warnings [1]. The calculations with
> default parameters start for neutral atoms, and have to evolve towards (in
> your case) ions. This takes many more than 20 iterations in some cases. It
> may take even longer if your case is antiferromagnetic, as you have (I
> believe) created a ferromagnetic starting point. When the scf has converged
> I would worry about a non positive definite density matrix.
>
> Having 4f electrons at the Fermi energy etc when you are far from
> converged is not surprising. Only the converged values have meaning. I
> would personally reduce the Nd RMT as you probably have O 2p states leaking
> in.
>
> [1] A non positive density matrix is not physically correct, but can
> happen during the mixing; there is nothing in the mathematics that forbids
> it. (There is an unrelated option to constrain this, but it is probably not
> needed.)
>
> _____
> Professor Laurence Marks
> "Research is to see what everybody else has seen, and to think what nobody
> else has thought", Albert Szent-Gyorgi
> www.numis.northwestern.edu
>
> On Fri, Jan 3, 2020, 03:31 Fan <fxinwei123 at gmail.com> wrote:
>
>> Thank you for your reply, Prof. Blaha. In fact, when I change parameters
>> in inorb, I always do 'rm case.dmat*' and 'rm case.vorb*' , so I think it
>> should not be the problem. But I do value your suggestions, so I started a
>> new session, only used the struct file of Nd4Ni3O8 which is attached here,
>> and then
>> init_lapw -b -rkmax 7.5 -numk 2000 -sp -vxc 5 -lvns 6
>> create inorb and indm by copying them from templates and modify them
>> accordingly
>> runsp_lapw -p -orb -i 200 -ec 0.0001 -cc 0.001 -NI
>> during the scf cycle, QTL-B warning appeared, but the value was very
>> small (2~3, still could be a trouble?), the density matrix warnings
>> appeared at about the 20th cycle and persisted.
>>
>> With regards.
>>
>> Fan
>>
>>
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