Hi, I optimized the S1/S0-MECP using the Penalty-constrained search algorithm with the SF-TDDFT method.
These are the optimized excited energies:
SF-DFT Excitation Energies
(The first “excited” state might be the ground state)
Excited state 1: excitation energy (eV) = 0.7779
Total energy for state 1: -1523.45110900 au
<S**2> : 1.2770
S( 2) → S( 2) amplitude = 0.9556 alpha
Excited state 2: excitation energy (eV) = 0.8837
Total energy for state 2: -1523.44722004 au
<S**2> : 0.9577
S( 1) → S( 1) amplitude = 0.9634 alpha
Excited state 3: excitation energy (eV) = 0.9304
Total energy for state 3: -1523.44550203 au
<S**2> : 0.1001
D( 134) → S( 1) amplitude = -0.1789
S( 2) → S( 1) amplitude = 0.9578 alpha
Excited state 4: excitation energy (eV) = 2.5970
Total energy for state 4: -1523.38425795 au
<S**2> : 0.1437
S( 1) → S( 2) amplitude = 0.9628 alpha
Determine which singlet state to optimize in UCIS or Spin-Flip UCIS
A threshold of <S**2> = 1.20 is used to identify singlet states
Excited state 1, <S^2> = 1.2770: is it a singlet? No.
Excited state 2, <S^2> = 0.9577: is it a singlet? YES.
Excited state 3, <S^2> = 0.1001: is it a singlet? YES.
Here, in the output, it shows that E.S. 2 and 3 are singlets.
Then, I ran the SA-SF-DFT job using the optimized coordinates at MECI to get the pure spin states.
Input:
$molecule
0 3
N 3.0961352442 4.2286446747 12.2482586833
C 1.2645468288 6.8378970956 7.7355190039
C 1.9366378273 6.6758198711 6.4527213416
C 2.7147940227 4.7337034120 11.0616143168
C 3.0188939736 4.2658277700 9.7648590265
H 3.6135666101 3.3672678052 9.6090657734
C 2.5629238263 5.0119538890 8.7063637120
H 2.7990492785 4.7486839882 7.6766210461
C 1.7266702467 6.1551871616 8.8954737889
C 1.4199898478 6.6047444211 10.2114222862
H 0.8416162118 7.5156695922 10.3624688920
C 1.9278817791 5.9200002724 11.2823978684
C 1.8545480980 6.0999371256 12.7231756054
C 1.2499206656 7.0480607793 13.5514664641
H 0.6957193804 7.8858899648 13.1262466705
C 1.3767811479 6.8970036551 14.9311880052
H 0.9153954339 7.6255795418 15.5990014884
C 2.0898559422 5.8166250800 15.4755512513
H 2.1705136920 5.7184604101 16.5593428104
C 2.6998491145 4.8609446323 14.6623297388
H 3.2450084053 4.0219187745 15.0946419156
C 2.5716714250 5.0268753179 13.2846911548
C 3.8442405466 2.9907610808 12.4468368030
H 4.4478238766 3.1073281162 13.3578232171
H 4.5479984202 2.8919890207 11.6105640730
C 2.9147229628 1.7809500034 12.5536792848
H 2.3236582145 1.7063442443 11.6246629110
H 2.1988411586 1.9641509976 13.3712119641
C 3.6563101165 0.4654861842 12.8038415317
H 4.2517954701 0.5475781786 13.7313955342
H 2.9001698528 -0.3127047124 12.9938229839
C 4.5661421367 0.0280375602 11.6515687799
H 5.3517967421 0.7855927411 11.4906559521
H 3.9751419971 -0.0048545998 10.7172899815
C 5.2423702754 -1.3305476009 11.8701026767
H 5.9787692045 -1.4889602467 11.0645975150
H 5.8212757009 -1.2999989640 12.8106309193
C 4.2785231987 -2.5175794480 11.9011197306
H 3.6746923885 -2.5574531562 10.9793212790
H 3.5836349334 -2.4628802190 12.7538095888
H 4.8268231824 -3.4686093687 11.9837641573
C 0.0505301782 7.6717113970 7.8698739031
C -0.1101486774 8.8577657667 7.1245624981
H 0.7243752446 9.2385349821 6.5402337753
C -1.3080789418 9.5574880344 7.1743073870
H -1.4084177917 10.4922420310 6.6216836095
C -2.3859099939 9.0593566122 7.9152771058
H -3.3323335357 9.6025109503 7.9306582525
C -2.2578911718 7.8646869846 8.6208672398
H -3.1044426186 7.4562473673 9.1736928611
C -1.0422250961 7.1826571356 8.6157617113
H -0.9623758394 6.2274170732 9.1361847730
C 1.2029854302 5.9072471989 5.4509837895
C 1.6774002552 5.7375190288 4.1177746705
H 2.6016413191 6.2317143155 3.8128819989
C 1.0293539967 4.9289655393 3.1908715408
H 1.4529423673 4.8448140886 2.1851691999
C -0.1331022108 4.2146421119 3.5192960717
H -0.6375455666 3.5826050998 2.7868105681
C -0.6053787681 4.3357601304 4.8229718391
H -1.4969583809 3.7835766689 5.1355946181
C 0.0340643714 5.1580472198 5.7591216242
H -0.3905562145 5.1854322952 6.7653228931
C 2.6876780433 7.9149696484 6.1938064222
C 2.6809477322 8.6312378062 4.9612650355
H 2.0901150440 8.2527357758 4.1269711518
C 3.3969421870 9.8106512374 4.7851579708
H 3.3608855606 10.3086980650 3.8116937807
C 4.1311162755 10.3867083969 5.8319866253
H 4.6788866434 11.3198469543 5.6903901630
C 4.1424679956 9.7214305116 7.0572464588
H 4.7071465929 10.1341932642 7.8981090178
C 3.4601077651 8.5151289265 7.2308884495
H 3.5389784244 8.0161323359 8.1993632662
$end
$rem
BASIS = cc-pVDZ
EXCHANGE = omegab97xd
OMEGA = 160
SASF_CIS = 1
unrestricted = false
cis_n_roots = 4
cis_triplets = TRUE
cis_SINGLETS = TRUE
SOLVENT_METHOD = PCM
$end
$solvent
DIELECTRIC 7.425700
OPTICALDIELECTRIC 1.974025
$end
These are the results:
SA-SF-RPA Excitation Energies
Excited state 1: excitation energy (eV) = 2.9703
Total energy for state 1: -1523.364773463938
Singlet
D(127) → S( 1) amplitude = -0.1549
D(134) → S( 1) amplitude = -0.2074
S( 2) → V( 8) amplitude = -0.2248
S( 2) → S( 1) amplitude = 0.9026
Excited state 2: excitation energy (eV) = 3.3144
Total energy for state 2: -1523.352129113124
Singlet
D(126) → S( 1) amplitude = 0.1592
D(134) → S( 2) amplitude = 0.1591
S( 1) → S( 1) amplitude = 0.6523
S( 2) → S( 2) amplitude = -0.6523
Excited state 3: excitation energy (eV) = 4.6752
Total energy for state 3: -1523.302120727783
Singlet
D(126) → S( 2) amplitude = -0.2558
S( 1) → V( 10) amplitude = -0.1926
S( 1) → S( 2) amplitude = -0.8901
Excited state 4: excitation energy (eV) = 4.8659
Total energy for state 4: -1523.295111670003
Singlet
D(127) → V( 1) amplitude = 0.1526
D(134) → V( 1) amplitude = 0.3071
D(134) → S( 2) amplitude = 0.1634
S( 2) → V( 1) amplitude = -0.8728
SA-SF-DFT results are not showing degeneracy. Can anyone suggest how I can figure out this spin-contamination problem?
Except MR-SFTDDFT because it is not implemented in Q-Chem.