Electronic structure of CeO2 greatly depends on initial guess of wave function in OT method

Florian Schiffmann flosch... at gmail.com
Tue Apr 7 05:37:54 UTC 2015


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 
   L 1
   N 2
   NEL 2
   L 1
   N 2
   NEL 2

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

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