[QE-developers] eigenstate calculated by QE

[Paolo Giannozzi]

If you repeat the same calculation, you get the same eigenvectors. Slightly
different calculations may actually give very similar eigenvectors, but
there is no guarantee.

Paolo

On Thu, Dec 9, 2021 at 8:55 PM 曾梓萌 <zengzm20 at mails.tsinghua.edu.cn> wrote:

> dear Paolo
>
> Thank you very much for your reply. I have done some tests on this issue
> and got some incomprehensible results. For a system with Kramer degeneracy,
> perform multiple calculations and draw the spatial distribution of an
> eigenstate. In repeated calculations, the spatial distribution of the
> states is almost the same. If in multiple calculations, the eigenstates
> calculated by QE are random (but orthonormal) linear combinations inside
> the degenerate subspace, then it seems that a consistent spatial
> distribution should not be obtained？
>
> Zeng Zimeng
>
> 在2021-12-09 18:14:45，Paolo Giannozzip.giannozzi at gmail.com写道：
>
> Hi
>
> if I understand correctly your question: yes, ALL degenerate eigenstates
> are random (but orthonormal) linear combinations inside the degenerate
> subspace. And no, typically they do not resemble  the eigenstates one would
> find in textbooks.
>
> Paolo
>
> On Thu, Dec 9, 2021 at 10:59 AM 曾梓萌 <zengzm20 at mails.tsinghua.edu.cn>
> wrote:
>
>> dear develpoers
>>
>> For Kramer's degenerate system, there are two energy degenerate
>> eigenstates on each k and E, and any linear combination of these two
>> degenerate states is still the eigenstate of the system. Is the eigenstate
>> calculated by QE this random linear combination eigenstate?
>>
>> I will appreciate any helps in this subject.
>> Truly yours,
>> Zeng Zimeng
>> Tsinghua university
>>
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>
>
> --
> Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
> Univ. Udine, via delle Scienze 206, 33100 Udine, Italy
> Phone +39-0432-558216, fax +39-0432-558222
>
>

-- 
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 206, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222
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