Molcas Forum

ka3

Member

Registered: 2026-03-24

Posts: 7

Density Differences Between Excited States

I wish to compute the density differences between two states to visualise the flow of electron density upon excitation. I'm aware pegamoid can do this for me, however in certain cases I wish to compute the differences between states of different symmetry - which I think means I can't use pegamoid for this. As such I've tried to compute the density differences between two example states (ground and first excited state) using the GRID_IT program (here the irreps of the states are the same - although this may not always be the case). I should also mention that these are RASSCF orbitals with core 2p orbitals in RAS1, all other orbitals are included in RAS2. My input is given below, here I read in the RasOrb orbitals for each root I'm interested, save them to a lus file and then compute the difference between them in a separate call to GRID_IT.

&GATEWAY
COORD = $CurrDir/../../../../thiophenol_gs.xyz
GROUP = Z
BASIS = ANO-RCC-VDZP
Douglas-Kroll
Verbose
RICD
BSShow

&SEWARD

&Grid_it
FileOrb=$CurrDir/valence-dz-a.RasOrb
>> COPY $Project.lus $CurrDir/S0_ORBS.lus

&Grid_it
FileOrb=$CurrDir/valence-dz-a.RasOrb.1
>> COPY $Project.lus $CurrDir/S1_ORBS.lus

&Grid_it
LUS1=$CurrDir/S0_ORBS.lus
LUS2=$CurrDir/S1_ORBS.lus
MINUS
NAME=Difference
>> COPY $Project.Difference.lus $CurrDir/$Project.Difference.lus

However this always gives me a not implemented error...

 Not implemented
Unrecognized keyword in input file:/HOM
--- Stop Module: grid_it at Mon Jun  1 14:47:56 2026 /rc=_RC_INPUT_ERROR_ ---

Ultimately I wish to visualise something like Fig. S1 in the SI of https://pubs.acs.org/doi/10.1021/jacs.5c04874. Is it also possible to compute the density differences between the hole and electron parts of NTO's calculated by RASSI? Or does this not make sense.

Any help would be greatly appreciated, thanks!

Ignacio

Administrator

From: Uppsala

Registered: 2015-11-03

Posts: 1,204

Re: Density Differences Between Excited States

It should be possible to view density differences (and NTOs) with RASSI and Pegamoid. See the naphthalene sample in https://gitlab.com/Jellby/Pegamoid/-/tr … r/samples/ If I remember correctly you need to use h5 files as input for RASSI, and the TDM keyword.

You could also save densities in cube format, and then perform the subtraction manually (which should be pretty easy).

ka3

Member

Registered: 2026-03-24

Posts: 7

Re: Density Differences Between Excited States

Thanks Ignacio, does the same apply to using caspt2 wavefunctions as well? I guess to do this in pegamoid I will need to ensure that RASSI reads in caspt2 wavefunctions from h5 and not from JobMix?

Ignacio

Administrator

From: Uppsala

Registered: 2015-11-03

Posts: 1,204

Re: Density Differences Between Excited States

Yes, it should. In order to get h5 files from CASPT2 you need to feed it h5 files too (with the FILE keyword).