negative homo - lumo gap

[Ian Hamilton]

Hi Marcella,

One of my students has encountered this problem. He tried changing the OT 
and increasing the number of MOs (we don't know what you mean by "smearing 
the occupation numbers around the Fermi energy") but it didn't correct the 
problem. I’m posting this on his behalf because he was unable to- he got a 
message that he had “limited access to public groups in his domain.”

Do you (or anyone else) have another suggestion? In his pdos files all the 
levels look fine except for the HOMO and LUMO.

>From his output:
 Fermi Energy [eV] :   -5.966796
  Lowest Eigenvalues of the unoccupied subspace spin            1
 -----------------------------------------------------
  Reached convergence in          149  iterations 
      -0.23489989     -0.21167052     -0.18538586     -0.17943768
      -0.13796253     -0.13007839
 HOMO - LUMO gap [eV] :   -0.425155
 ENERGY| Total FORCE_EVAL ( QS ) energy (a.u.):           
 -1076.972424168399129

Best regards,
Ian Haminton

On Sunday, November 22, 2009 at 6:13:06 AM UTC-5, Claudio wrote:
>
> Dear all, 
>
> sometimes after I converge a calculation to an accuracy of say 1.0E-5 
> I get things like 
>
> HOMO - LUMO gap [eV] :   -0.980594 
>
> This is because the Homo Energy is 0.22417642 and the Lumo Energy is 
> 0.18814027 in AU. 
>
> I have requested the same accuracy for homo and lumo  and have added 
> enough iterations to the lumo calculation loop to make sure the 
> program claims it is converged. I am using the OT method. How do I 
> prevent this from happening? I mean how do I ensure that the 
> calculation yields Lumo energies that are higher than the homo energy? 
>
>
> Sorry to bother you and thanks for your help! 
>
> Claudio 
>
>
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