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#1 2018-08-31 10:45:29

Tian Lu (Multiwfn developer)
From: Beijing
Registered: 2017-09-11
Posts: 138

Calculate transition dipole moments between excited states for ORCA

I noticed that in ORCA forum there is a user asked how to calculate transition dipole moments between excited states with TDDFT using ORCA

I'm pretty new to TD-DFT and I'm currently working on silicon quantum dots passivated with hydrogen (ranging from 40 to 250 atoms), trying to determine the transition dipole moments between electronically excited states. I didn't find any information about how to proceed in order to obtain them (I just got the absorption spectrum, which only shows the transition between the ground state and each individual excited state). Is this feasible or did I miss something ?

Unfortunately, current ORCA doesn't have this feature. However, using Multiwfn, this can be easily done. Below is my reply, I copy it here since some other Multiwfn/ORCA users may have the same problem.

Current latest version, namely version 3.6(dev) of Multiwfn is able to calculate transition dipole moment between excited states based on ORCA output.

First, conduct a CIS or TDA-DFT calculation using keywords like below, assume that file name is test.inp
! PBE0 def2-SVP nopop pal4
nroots 4
tprint 1E-8

Then use such as "orca_2mkl test -molden" command to convert test.gbw to test.molden.input

Finally, boot up Multiwfn and input
test.molden.input // The .molden input file
18 // Electronic excitation analyses
5 // Calculate transition electric dipole moments between all excited states
test.out // The ORCA output file
1 // Output transition dipole moments to screen
Now you will find below result on screen.

Ground state dipole moment in X,Y,Z:   -0.271701   -0.314645    0.344277 a,u,

Transition dipole moment between excited states (a.u.):
     i     j         X             Y             Z        Diff.(eV)   Oscil.str
     1     1    -1.7862676    -0.2640772     0.2405912     0.00000     0.00000
     1     2     0.1976941     0.0854227     0.0346682     0.70800     0.00083
     1     3     2.1779748    -0.1165127     0.1223195     1.38100     0.16146
     1     4    -0.4226960     0.0657206    -0.0047136     1.73500     0.00778
     2     2    -2.6132918    -0.1285522     0.0996265     0.00000     0.00000
     2     3     0.0625351     0.3407469    -0.0481496     0.67300     0.00202
     2     4     0.2904364    -0.1027734    -0.2020122     1.02700     0.00341
     3     3    -2.9400691    -0.2538387     0.1676538     0.00000     0.00000
     3     4     0.4640359     0.0322024    -0.0096710     0.35400     0.00188
     4     4     2.3204590     1.0665381    -0.2011480     0.00000     0.00000

The i and j are excited state indices, the line such as i=2 and j=2 corresponds to electronic dipole moment of excited state 2.

This feature of Multiwfn should work perfectly for CIS and TDA-DFT. However, for the TDHF or TDDFT, the result may be not always reliable, since in this case, current version of ORCA does not output excitation configuration coefficients and de-excitation configuration coefficients separately, which are needed for strictly evaluating transition dipole moments.


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