[Wien] density matrix is not positive

[Laurence Marks]

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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