[CP2K:6353] Re: Electronic structure of CeO2 greatly depends on initial guess of wave function in OT method

Lei Li leili... at gmail.com
Tue Apr 7 18:00:12 CEST 2015


Hi, Florian,

Thanks great for your suggestion.

I have tried broken symmetry for Ce with 'scf_guess' set as 'atomic'. But
the situation is same to what I got from calculation without Ce (total
energy ~0.86 eV higher than the restart situation)
Here are the parameters I used. Could you check if they look good? First
time to use broken symmetry. Also, I will try to add it for O.
For two Ce atoms next-nearby the oxygen vacancy, I tried the following
setting to make it Ce3+.
       &BS
         &ALPHA
           NEL -2   -1  1
           L    0   2   3
           N    6   5   4
         &END
         &BETA
           NEL -2  -1   -1
           L    0   2   3
           N    6   5   4
         &END
       &END
But for other Ce atoms, I used the following setting to make it Ce4+.
       &BS
         &ALPHA
           NEL -2   -1  -1
           L    0   2   3
           N    6   5   4
         &END
         &BETA
           NEL -2  -1   -1
           L    0   2   3
           N    6   5   4
         &END
       &END

Thanks!

Best.


On Tue, Apr 7, 2015 at 12:37 AM, Florian Schiffmann <flosch... at gmail.com
> wrote:

> Hi,
>
> that makes it more clear. As I am not 100% sure what is going on I will
> have to do some guesswork.
>
> From your input you run an unrestricted calculation. In the atomic guess,
> CP2K still uses the restricted atomic orbitals as initial guess for both
> alpha and beta. This might lead to a situation where you have 0.5 of an
> electron initially sitting in the orbital affected by the U correction. As
> far as I remember te U correction is symmetric at this point and it might
> be arbitrary whether the orbital gets further filled or emptied due to the
> penalty function (therefore there is some arbitraryness in your result). I
> think this is somewhat general that the U term can lock you in a given
> state depending on your initial guess.
>
> Could you try to use a broken symmetry guess in your calculation where you
> initialize O as 2-  and Ce as 4+ and see how the energy is affected?
> For O this chould look like
> &BS
> &ALPHA
>    L 1
>    N 2
>    NEL 2
> &END
>  &BETA
>    L 1
>    N 2
>    NEL 2
> &END
> &END
>
> For Ce it is a bit more complicated. simply remeber, that cp2k puts a
> closed shell wfn in alpha and beta. Therefore NEL in this case is 2 as the
> closed shell representation of a 2p3 is a 2p6 wfn.
>
> Hope that helps
>
> Flo
>
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-- 
Best,
Lei

University of Nebraska - Lincoln,
Department of Chemistry,
536 Hamilton Hall.
Lincoln, NE 68588
Phone: 402-853-8119
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