RAS-2SF Exciton decomposition

young · December 8, 2021, 8:40am

Hello,
I would like to ask how to decompose the exciton state using the RAS-2SF method.

I watched the video [Webinar 59 Restricted Active Space CI family of methods in Q Chem].
It helps a lot in learning new method.
In video time 49:23, it elucidates the RASCI method can decompose the exciton states to LE, CR, and ME.

I wanted to try this RAS-2SF calculation to study the characters of exciton states.
I followed the Q-Chem manual to perform RAS-2SF calculation for tetracene dimer using quintet reference.
My input file is below.

However, I cannot find the decomposition percent of LE, CR, ME of exciton states in output file.
The video and the reference said the spin and charge cumulants are needed.

To include the spin and charge cumulants and obtain the decomposition percent of LE, CR, ME of exciton states,

Do I need to include other options in the input file?
or
Do I need additional computational (calculation) coding (matlab, python, etc) after the RASCI calculation?
Or
Do I miss something important in output file?

I’m new to Q-Chem so it is difficult to me.
please help me.

Thanks a lot

Input file:

$molecule
0 5
C -0.5790000 -1.8650000 -4.7370000
C -1.2680000 -1.8240000 -3.5680000
C -0.5790000 -1.8320000 -2.3500000
C 0.5790000 -1.8320000 -2.3500000
C 1.2680000 -1.8240000 -3.5680000
C 0.5790000 -1.8650000 -4.7370000
C -1.2820000 -1.7900000 -1.1390000
C 1.2820000 -1.7900000 -1.1390000
C 0.8170000 -1.8500000 0.0000000
C -0.8170000 -1.8500000 0.0000000
C -1.2820000 -1.7900000 1.1390000
H -2.3550000 -1.7190000 1.2860000
C -0.5790000 -1.8320000 2.3500000
C 0.5790000 -1.8320000 2.3500000
C 1.2820000 -1.7900000 1.1390000
H -2.3550000 -1.7190000 -1.2860000
H -1.1090000 -1.8580000 -5.6670000
H -2.3370000 -1.7850000 -3.5780000
H 2.3370000 -1.7850000 -3.5780000
H 1.1090000 -1.8580000 -5.6670000
H 2.3550000 -1.7190000 -1.2860000
H 2.3550000 -1.7190000 1.2860000
C 1.2680000 -1.8240000 3.5680000
C 0.5790000 -1.8650000 4.7370000
C -0.5790000 -1.8650000 4.7370000
C -1.2680000 -1.8240000 3.5680000
H 2.3370000 -1.7850000 3.5780000
H 1.1090000 -1.8580000 5.6670000
H -1.1090000 -1.8580000 5.6670000
H -2.3370000 -1.7850000 3.5780000
C -0.5790000 1.8650000 -4.7370000
C -1.2680000 1.8240000 -3.5680000
C -0.5790000 1.8320000 -2.3500000
C 0.5790000 1.8320000 -2.3500000
C 1.2680000 1.8240000 -3.5680000
C 0.5790000 1.8650000 -4.7370000
C -1.2820000 1.7900000 -1.1390000
C 1.2820000 1.7900000 -1.1390000
C 0.8170000 1.8500000 0.0000000
C -0.8170000 1.8500000 0.0000000
C -1.2820000 1.7900000 1.1390000
H -2.3550000 1.7190000 1.2860000
C -0.5790000 1.8320000 2.3500000
C 0.5790000 1.8320000 2.3500000
C 1.2820000 1.7900000 1.1390000
H -2.3550000 1.7190000 -1.2860000
H -1.1090000 1.8580000 -5.6670000
H -2.3370000 1.7850000 -3.5780000
H 2.3370000 1.7850000 -3.5780000
H 1.1090000 1.8580000 -5.6670000
H 2.3550000 1.7190000 -1.2860000
H 2.3550000 1.7190000 1.2860000
C 1.2680000 1.8240000 3.5680000
C 0.5790000 1.8650000 4.7370000
C -0.5790000 1.8650000 4.7370000
C -1.2680000 1.8240000 3.5680000
H 2.3370000 1.7850000 3.5780000
H 1.1090000 1.8580000 5.6670000
H -1.1090000 1.8580000 5.6670000
H -2.3370000 1.7850000 3.5780000
$end

$rem
AUX_BASIS = rimp2-cc-PVDZ
BASIS = cc-pVDZ
CORRELATION = RASCI2
EXCHANGE = HF
GUI = 2
RAS_ACT_DIFF = 0
RAS_ACT_OCC = 2
RAS_ACT_VIR = 2
RAS_N_ROOTS = 8
SET_ITER = 25
UNRESTRICTED = 0
MAX_SCF_CYCLES = 10000
SYMMETRY = false
MEM_STATIC = 10000
$end

dcasanova · December 10, 2021, 12:13pm

Dear young,

the decomposition analysis for rasci wave functions is only available for the implementation with analytical integrals. For that, you must use CORRELATION = RASCI (insteat of RASCI2).
Additional details for the fragment model are defined by the keywords:
RAS_NFRAG n ! n number of fragments
RAS_NFRAG_ATOMS [i,j,k…] ! number of atoms in each fragment.
RAS_FRAG_SETS [i,j,k…] ! (optional) number of orbitals in each orbital set to perform orbital localization.

Please, see sections 7.12.4 and 7.12.8 of the manual for further details (7.12.8 Job Control for the RASCI1 Implementation‣ 7.12 Restricted Active Space Spin-Flip (RAS-SF) and Configuration Interaction (RAS-CI) ‣ Chapter 7 Open-Shell and Excited-State Methods ‣ Q-Chem 5.4 User’s Manual).

Hence, you basically need to perform some small changes in your input file.
Please, let me know if it works.

Thanks a lot.
Best regards,
David

young · December 15, 2021, 1:30am

Thank you so much, David

Thanks to you, I was able to see the decomposition percent of exciton state in the output file.

In manual chapter 7.12.8, ‘RAS_OCC’ is described as initial doubly occupied orbitals before including hole type of excitation.

I thought that if the dimer has 24 electrons and ‘RAS_ELEC’(RAS2) is 4, then remaining 20 electrons in RAS1.

Thus, ‘RAS_OCC’ is 10
And ‘RAS_FRAG_SETS’ [core orbital of RAS1, residual RAS1, RAS2, RAS2]

Is it right?
or
Is there a criterion for determining ‘RAS_OCC’ and ‘RAS_FRAG_SETS’?

And is there a method to frozen the core orbital of RAS1?

I appreciate your help so much.

dcasanova · December 15, 2021, 4:11am

Dear Young,

yes, ‘RAS_OCC’ 10 should be correct in this case.
Then, ‘RAS_FRAG_SETS’ [core orbital of RAS1, residual RAS1, RAS2, RAS3] seems a good option, but you can also play with other schemes of orbital localization by splitting it in smaller groups. E.g.,
[core orbital of RAS1, residual RAS1, RAS2,RAS2’, RAS3,RAS3’,RAS3’’].

You can froze core (from the lowest energy one) and virtual (from the highest energy one) orbitals with:
N_FROZEN_CORE ‘N_core’
N_FROZEN_VIRTUAL ‘N_virtual’

These orbitals will not be considered in the RASCI wavefunction.
I hope this will help.

Thank you very much!
David