We are calculating the Franck-Condon factors for vibrationally resolved spectra. I successfully ran calculations using B3LYP on a reference BODIPY molecule, but I’m encountering issues when applying the LRC-wPBE functional to the DPz molecule
1.Ground and Excited State Geometry Verification:
When using LRC-wPBE to verify the minima of the ground and excited state geometries, I get large imaginary frequencies (up to 1100i) that seem unreasonable. In contrast, both B3LYP and wB97X-D give no imaginary frequencies for the same geometries. The only way I’ve been able to get reasonable frequencies with LRC-wPBE is by switching to numerical frequency calculations. Since LRC-wPBE is a range-separated functional like wB97X-D, I didn’t expect this behavior. Is there a known issue with analytic frequency calculations using LRC-wPBE in Q-Chem?
2. Running the numerical Franck-Condon calculations with LRC-wPBE gave unusual results, which I suspect might be related to the frequency calculation issue. Has anyone encountered similar problems with LRC-wPBE in Franck-Condon calculations？
Can you please provide the complete input for one of these frequency calculations that affords the large imaginary frequency? (For our convenience, please give us the optimized geometry.) Use the </> key in this GUI to paste your input file.
Sure：here is the .in
$COMMENT
27-0-DPZ_num_freq
RUN freq validation with numerical deritive
$END
$REM
! This is the command calling for numerical dev
ideriv = 1
! This is the freq step of calculated Hessian opt of GS geometry
MEM_TOTAL 250000
JOBTYPE FREQ
GEOM_PRINT TRUE
EXCHANGE GEN
BASIS 6-31g*
LRC_DFT TRUE
OMEGA 170
INTEGRAL_SYMMETRY FALSE
POINT_GROUP_SYMMETRY FALSE
$END
$XC_FUNCTIONAL
! Stands for LRC-wPBE
C PBE 1.00
X wPBE 1.00
$END
$MOLECULE
0 1
C -1.5085568938 0.9438650721 0.7927125209
N -2.8653891283 0.9432016260 0.8051274411
C -3.4993560273 0.0300282530 0.0210199471
C -2.7436571153 -0.8619966861 -0.8175956650
N -1.3938167132 -0.8712434872 -0.8098745365
C -0.7508062402 0.0197667107 0.0064465515
N 4.9471294874 0.0065142689 -0.0072165146
C 5.7894454802 1.1740245335 0.0307426841
C 5.8025947202 -1.1552568261 -0.0244407800
N -4.9321077342 0.0149952733 0.0368442816
C -7.9263666327 3.1058770181 -0.0120996362
C -8.2103022980 1.7056530204 -0.0410941878
C -7.1598170540 0.7463260024 -0.0099076139
C -5.7882251109 1.1764028223 0.0553219475
C -5.4733818884 2.5620988960 0.0859078336
C -6.5442197035 3.4973958919 0.0489608051
C -7.1525017431 -0.7369987110 -0.0350814122
C -8.1926818928 -1.7068799696 -0.0495376714
C -7.8972327138 -3.1054034225 -0.0176481865
C -6.5127169188 -3.4844100211 0.0439332323
C -5.4510764217 -2.5367777788 0.0573583186
C -5.7740462392 -1.1529512102 -0.0010185632
C -9.1152190398 4.1513361046 -0.0421613746
C -9.0770857269 -4.1609651303 -0.0354903616
C -9.9585622043 3.9601646610 -1.3696475615
C -10.0527033489 3.9237439122 1.2144313405
C -8.6091802088 5.6450837380 -0.0028671748
C -10.0083407700 -3.9370386097 1.2264743102
C -9.9301795938 -3.9810851345 -1.3581829704
C -8.5575465886 -5.6500426842 0.0054604835
C 5.4671669017 2.5580038526 -0.0287788153
C 6.5291644727 3.5051434920 -0.0149729132
C 7.9135185133 3.1255632424 0.0480158160
C 8.2083326856 1.7269723667 0.0809908127
C 7.1677236742 0.7575019447 0.0662439529
C 7.1743846110 -0.7257923484 0.0418318350
C 8.2243943559 -1.6856146198 0.0742815379
C 7.9398391085 -3.0856847832 0.0454175789
C 6.5575216405 -3.4765817595 -0.0166052642
C 5.4871629862 -2.5408333188 -0.0548316535
C 9.1281724285 -4.1317229619 0.0765208523
C 10.0657100095 -3.9056999731 -1.1803250869
C 9.9716480853 -3.9398174164 1.4037871658
C 8.6213599633 -5.6252412993 0.0386864638
C 9.0938235843 4.1806336072 0.0661053123
C 9.9458856901 4.0011415319 1.3895069375
C 10.0258603014 3.9555291040 -1.1950549962
C 8.5749516582 5.6699132882 0.0238521289
C 2.7588358295 0.8839513542 0.8474185101
N 1.4088704506 0.8931966670 0.8398883407
C 0.7657663991 0.0024972252 0.0234521093
C 1.5234245132 -0.9211983320 -0.7635118942
N 2.8801914181 -0.9207150107 -0.7759099233
C 3.5142223410 -0.0079882015 0.0086657827
H -0.9925376863 1.6954280983 1.4279200379
H -3.2516818423 -1.5619134267 -1.5164557708
H -9.2588297975 1.3428689689 -0.0901152085
H -4.4276389542 2.9161722405 0.1559404371
H -6.2711929308 4.5709211262 0.0776547150
H -9.2451888379 -1.3535366764 -0.0755351682
H -6.2289168214 -4.5544470636 0.0891750839
H -4.4051207239 -2.8972668114 0.1286520213
H -10.4045110013 2.9357264523 -1.4421772719
H -9.3199471199 4.1171049284 -2.2775894953
H -10.8027910030 4.6980237884 -1.4095562168
H -10.5026279989 2.8984996320 1.2242546719
H -10.8977475681 4.6618771450 1.2152959865
H -9.4812864342 4.0525455739 2.1702478993
H -7.9630043158 5.8940220968 -0.8837365392
H -8.0291918780 5.8690549619 0.9291832500
H -9.4857484769 6.3431965264 -0.0253152968
H -10.4685244450 -2.9163971078 1.2351181020
H -9.4295628147 -4.0563408323 2.1790788044
H -10.8459435330 -4.6834285981 1.2356975252
H -10.3835678466 -2.9600224968 -1.4319726398
H -10.7695725408 -4.7248017192 -1.3895898100
H -9.2965106677 -4.1374746236 -2.2696786323
H -7.9732107720 -5.8673164247 0.9364701861
H -7.9117164730 -5.8949852338 -0.8768229902
H -9.4278005446 -6.3560413444 -0.0128800136
H 4.4213915980 2.9188737026 -0.1012135557
H 6.2458794023 4.5752725364 -0.0612272992
H 9.2606553469 1.3731498753 0.1080572059
H 9.2730391710 -1.3232417842 0.1238823999
H 6.2839984370 -4.5499830337 -0.0452334131
H 4.4412891127 -2.8944670997 -0.1255803560
H 10.5160049085 -2.8806236896 -1.1910027809
H 9.4941755966 -4.0350652163 -2.1359876422
H 10.9104290647 -4.6442106232 -1.1805941818
H 10.4182091564 -2.9155921087 1.4754908691
H 10.8154886656 -4.6780860766 1.4442711285
H 9.3329994517 -4.0956846157 2.3118945030
H 8.0417571026 -5.8500225657 -0.8934047451
H 7.9745737773 -5.8727775488 0.9195083626
H 9.4975463521 -6.3237940475 0.0623895831
H 10.3987821909 2.9799189992 1.4641594581
H 9.3116475596 4.1582551648 2.3004801320
H 10.7855676750 4.7445194455 1.4211368412
H 10.4857431321 2.9347452422 -1.2026697397
H 10.8637093452 4.7016481054 -1.2042901956
H 9.4477433583 4.0743120866 -2.1481259027
H 7.9288487006 5.9157598165 0.9056798795
H 7.9911160358 5.8867687656 -0.9075658943
H 9.4454918852 6.3755547982 0.0421054405
H 3.2668105691 1.5838118457 1.5463375673
H 1.0072456295 -1.6723955136 -1.3990398391
$END
Using your coordinates and the following $rem section
$REM
!ideriv = 1
MEM_TOTAL 250000
JOBTYPE opt
GEOM_PRINT TRUE
EXCHANGE GEN
BASIS 6-31g*
LRC_DFT TRUE
OMEGA 170
INTEGRAL_SYMMETRY FALSE
POINT_GROUP_SYMMETRY FALSE
$END
$XC_FUNCTIONAL
! Stands for LRC-wPBE
C PBE 1.00
X wPBE 1.00
$END
I get the following after one opt step:
Step 1 :
Energy is -2186.6103871650
Maximum Tolerance Converged?
Gradient 1.08413320e-02 3.00000000e-04 false
Displacement 2.05390598e-01 1.20000000e-03 false
Energy change 4.76758347e-02 1.00000000e-06 false
Therefore, it looks to me like your geometry is not converged at a consistent level of theory. That would account for a large imaginary frequency.
UPDATE: Mine went for 7 optimization cycles starting from the geometry that you provided.
Thank you, Dr. Herbert!
I’m the undergraduate student working on this project. I re-optimized the structure using stricter convergence criteria and recalculated the vibrational frequencies with LRC-wPBE. Unfortunately, I still observed several high imaginary frequencies, with the highest being 1172.18i, which seems unusually high based on my current understanding.
In comparison, when using wB97X-D and CAM-B3LYP on the same structure, no imaginary frequencies were predicted, the lowest vibrational frequency is about 25 cm^-1. Since there is a great difference between these methologies, I’m wondering if there might be a bug or some issue specific to LRC-wPBE in this context?
I’ve uploaded the related input and output files here for reference: QChem_LRC-wPBE_Problem - Google Drive
I would greatly appreciate any insights or feedback you may have!
I think there is probably some inconsistency that you are missing, because my point was that the structure that you provided (which was ostensibly already minimized at the LRC-wPBE level) did not appear to be very close at all to being minimized. This feels like a question for your research advisor.