[CPMD-list] TDDFT force calculation not compatible with NLCC pseudopotential?

[Juerg Hutter]

Hi

one of the problems of TDDFT geometry optimization is
that you might get into areas where the geometry is far
of the optimal ground state geometry. In those cases
(restricted) Kohn-Sham calculations for the ground state
are difficult and might result in unreasonable
electronic structures.

I would check the ground state result, especially
HOMO and LUMO energy for your last geometry.

regards

Juerg Hutter

----------------------------------------------------------
Juerg Hutter                   Phone : ++41 44 635 4491
Physical Chemistry Institute   FAX   : ++41 44 635 6838
University of Zurich           E-mail: hutter at pci.uzh.ch
Winterthurerstrasse 190
CH-8057 Zurich, Switzerland
----------------------------------------------------------


On Mon, 25 Jun 2007, Hua Bao wrote:

> Dear All,
>
> I am calculating Ti[H2O]6 cluster with TDDFT. The spectra result is pretty
> good. However, TDDFT MD result is not reasonable. It has following warning
> messages while calculating the TDDFT forces (also see my last post),
>
> CALCULATION OF TDDFT FORCES
>
> CPU TIME FOR INITIALIZATION OF LINEAR RESPONSE:     0.17 SECONDS
> WARNING! First order density integral (R space)   1.40622137E-06
> WARNING! First order density integral (R space)   3.17749222E-04
>   NFI      GEMAX     CNORM         ETOT(2)        DETOT     TCPU
>     1***********547.690471****************    0.000       37.130
> WARNING! First order density integral (R space)   1.05641421E-03
>
> And the force is unreasonable (10^3 order). I am using Ti_MT_LDA_NLCC
> pseudopotential and LDA functional. If I don't specify the pseudopotential
> option of NLCC, then it will run normally. However, the electron spectra
> result is not good. Is there any incompatible between NLCC and TDDFT force
> calculation?
>
> If it is the case, can anyone give me some suggestions on choosing a proper
> pseudopotential of Titanium? There is only NLCC pseudopotential for Ti in
> CPMD package.
>
> Thanks,
> Hua Bao
>
> Graduate Student
> School of Mechanical Engineering
> Purdue University
> Office Tel: (765) 494-6944
>
>