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How do you calculate the change in dipole moment from the ground to first excited state using ORCA? I have done DFT to get the dipole moment at the ground state and TDDFT of this neutral molecule. How would I get the dipole moment of the first excited state though? I have tried using the keywords to test it out from the ORCA input library example:

! Engrad Keepdens
%maxcore 1000
%tddft
  nroots 5 #number of states to be computed
  Iroot 2 #electing the excited state
  end

However in my output file I got two dipole moments. Is one of these the dipole moment of the second excited state?

                            ***************************************
                            *     ORCA property calculations      *
                            ***************************************

                                    ---------------------
                                    Active property flags
                                    ---------------------
   (+) Dipole Moment


------------------------------------------------------------------------------
                       ORCA ELECTRIC PROPERTIES CALCULATION
------------------------------------------------------------------------------

Dipole Moment Calculation                       ... on
Quadrupole Moment Calculation                   ... off
Polarizability Calculation                      ... off
GBWName                                         ... AQx.gbw
Electron density file                           ... AQx.scfp
The origin for moment calculation is the CENTER OF MASS  = (19.676450, -8.066302 -0.130676)

-------------
DIPOLE MOMENT
-------------
                                X             Y             Z
Electronic contribution:     59.75528      40.37126      28.07622
Nuclear contribution   :    -60.31050     -43.16268     -30.49310
                        -----------------------------------------
Total Dipole Moment    :     -0.55522      -2.79142      -2.41688
                        -----------------------------------------
Magnitude (a.u.)       :      3.73385
Magnitude (Debye)      :      9.49069



--------------------
Rotational spectrum 
--------------------
 
Rotational constants in cm-1:     0.001089     0.000336     0.000262 
Rotational constants in MHz :    32.661377    10.062791     7.849287 

 Dipole components along the rotational axes: 
x,y,z [a.u.] :     2.336172    -2.544708    -1.417172 
x,y,z [Debye]:     5.938077    -6.468135    -3.602164 

 

                        *** CIS RELAXED DENSITY ***

------------------------------------------------------------------------------
                       ORCA ELECTRIC PROPERTIES CALCULATION
------------------------------------------------------------------------------

Dipole Moment Calculation                       ... on
Quadrupole Moment Calculation                   ... off
Polarizability Calculation                      ... off
GBWName                                         ... AQx.gbw
Electron density file                           ... AQx.cisp
The origin for moment calculation is the CENTER OF MASS  = (19.676450, -8.066302 -0.130676)

-------------
DIPOLE MOMENT
-------------
                                X             Y             Z
Electronic contribution:     59.47513      39.61229      27.69494
Nuclear contribution   :    -60.31050     -43.16268     -30.49310
                        -----------------------------------------
Total Dipole Moment    :     -0.83537      -3.55038      -2.79817
                        -----------------------------------------
Magnitude (a.u.)       :      4.59704
Magnitude (Debye)      :     11.68475



--------------------
Rotational spectrum 
--------------------
 
Rotational constants in cm-1:     0.001089     0.000336     0.000262 
Rotational constants in MHz :    32.661377    10.062791     7.849287 

 Dipole components along the rotational axes: 
x,y,z [a.u.] :     2.884110    -3.245341    -1.510784 
x,y,z [Debye]:     7.330824    -8.249002    -3.840108
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  • $\begingroup$ I think all of the questions were so tightly coupled that answering one answered them all. $\endgroup$
    – Tristan Maxson
    Commented Oct 6, 2020 at 20:28

1 Answer 1

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This second dipole moment is almost surely the excited state. You can see the nuclear contributions are identical and the rotational constants are also the same. This means they are both calculations of the same geometry. You can also see the magnitude of the dipole moment increases in the second calculation. This is very common in excited states.

The ORCA documentation also seems to state that *** CIS RELAXED DENSITY *** indicates this is the TD-DFT dipole moment. I suspect both the excited and ground state are output. If you change the Iroot option you may get different excited state dipole moments, I am not sure if the Iroot 2 corresponds to the first or second excited state. You should check this.

Disclaimer: I have never used ORCA.

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    $\begingroup$ In addition, note the file names listed as Electron density file. $\endgroup$
    – TAR86
    Commented Oct 6, 2020 at 16:49

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