[DFTB-Plus-User] Excited State Geometry Optimization - Insufficent single particle excitations

[Bálint Aradi]

Dear Mariana,

the problem is the finitness of your basis. For the H2O, you would have
6 basis functions only (one s orbital on each H and s, px, py, pz on the
O). With 8 electrons in the system, this results in 4 occupied and 2
empty molecular orbitals, and consequently there are only 4 x 2 = 8
excitations (from occupied orbital into unoccupied orbita) possible.

Best regards,

Bálint


On 15.12.20 08:51, Mariana Casal wrote:
> Hello everyone, 
> I am new to DFTB+. I downloaded the binaries from the website and I have
> been trying to do an excited state geometry optimization on water, but I
> get the error below. I am also attaching the input to this message.
> Would you have any insights into what I could be doing wrong?
> 
> Thank you very much, 
> Mariana Casal.
> 
> - OUTPUT - 
> 
> ***  Geometry step: 0
> 
>  iSCC Total electronic   Diff electronic      SCC error
>     1    0.00000000E+00    0.00000000E+00    0.78799432E+00
>     2   -0.41078116E+01   -0.41078116E+01    0.58416141E+00
>     3   -0.41111761E+01   -0.33645073E-02    0.45171409E-02
>     4   -0.41153649E+01   -0.41887901E-02    0.32166388E-04
>     5   -0.41153652E+01   -0.25640242E-06    0.12091839E-08
>>> Charges saved for restart in charges.bin
> ERROR!
> ->  Insufficent single particle excitations, 8, for required number of
> excited states 10
> Note: The following floating-point exceptions are signalling:
> IEEE_OVERFLOW_FLAG IEEE_UNDERFLOW_FLAG IEEE_DENORMAL
> 
> - INPUT - 
> 
> Geometry = xyzFormat {
>  <<< "h2o.xyz <http://h2o.xyz>"
> }
> 
> Driver = ConjugateGradient {
>   MovedAtoms = 1:-1
>   MaxForceComponent = 1E-4
>   MaxSteps = 100
>   OutputPrefix = "geom.out"
>   AppendGeometries = yes
> }
> 
> Hamiltonian = DFTB {
>   Scc = Yes
>   SlaterKosterFiles {
>     O-O =
> "/home/mariana/programs/dftbplus-20.2.1.x86_64-linux/dftbplus-20.2.1/slakos/3ob-3-1/O-O.skf"
>     O-H =
> "/home/mariana/programs/dftbplus-20.2.1.x86_64-linux/dftbplus-20.2.1/slakos/3ob-3-1/O-H.skf"
>     H-O =
> "/home/mariana/programs/dftbplus-20.2.1.x86_64-linux/dftbplus-20.2.1/slakos/3ob-3-1/H-O.skf"
>     H-H =
> "/home/mariana/programs/dftbplus-20.2.1.x86_64-linux/dftbplus-20.2.1/slakos/3ob-3-1/H-H.skf"
>   }
>   MaxAngularMomentum {
>     O = "p"
>     H = "s"
>   }
> 
> ExcitedState = Casida {
>   Symmetry = singlet
>   NrOfExcitations = 10
>   StateOfInterest = 1 #S1 = 1
>   WriteTransitions = yes
>   WriteCoefficients = yes
>   WriteEigenvectors = yes
>   WriteTransitionDipole = yes
>   WriteMulliken = yes
> }
> 
> Options {
>   WriteDetailedXML = yes
>   WriteResultsTag = yes
>   WriteDetailedOut = yes
> }
> 
> 
> Analysis {
>   WriteEigenvectors = yes
>   EigenvectorsAsText = yes
>   CalculateForces = Yes
> }
> 
> ParserOptions {
>   ParserVersion = 7
> }
> 
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> 


-- 
Dr. Bálint Aradi
Bremen Center for Computational Materials Science, University of Bremen
http://www.bccms.uni-bremen.de/cms/people/b-aradi/


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