I was wondering if there is a webinar or more information available on how to run a TDDFT calculation that captures shifts in absorbance energy that stems from solvent. My group is trying to compare the absorbance energies for terphenyl in different solvents to experimental results that show solvatochromism. It’s important we capture the effects of solvent on these systems because our relaxation following excitation should reflect exciplex behavior. The manual includes using non-eq PCM to calculate absorption energies (12.2.3 PCM Job Control‣ 12.2 Chemical Solvent Models ‣ Chapter 12 Molecules in Complex Environments: Solvent Models, QM/MM and QM/EFP Features, Density Embedding ‣ Q-Chem 5.2 User’s Manual, example 12.8) that seems to most closely match descriptions in benchmark papers. When we run this calculation for our system, we don’t seem to capture the solvent effect on absorption energy. A sample input file is here:
$molecule
0 1
C 3.3266531 -0.3872080 -0.6551596
C 3.9696785 -0.6918388 -1.8556737
H 3.3996852 -0.7258715 -2.7761372
C 5.3272092 -0.9721559 -1.8838935
H 5.8052500 -1.2129273 -2.8254316
C 6.0694459 -0.9536360 -0.7111066
H 7.1297414 -1.1727681 -0.7329091
C 5.4418474 -0.6518237 0.4896445
H 6.0119410 -0.6288289 1.4101971
C 4.0841214 -0.3712653 0.5168610
H 3.6110337 -0.1193560 1.4582652
C 1.8748147 -0.0892342 -0.6281747
C 1.2690761 0.6322337 -1.6565563
H 1.8690539 1.0061464 -2.4771633
C -0.0873420 0.9071973 -1.6343839
H -0.5203956 1.4895238 -2.4384699
C -0.8927391 0.4720839 -0.5823943
C -0.2869953 -0.2494341 0.4460095
H -0.8870148 -0.6233521 1.2665795
C 1.0693930 -0.5243714 0.4238437
H 1.5024591 -1.1067354 1.2278927
C -2.3445945 0.7699452 -0.5553792
C -2.9877076 1.0742487 0.6451726
H -2.4177811 1.1081529 1.5656829
C -4.3452734 1.3543756 0.6733884
H -4.8233907 1.5948695 1.6149590
C -5.0874623 1.3360462 -0.4994395
H -6.1477936 1.5549997 -0.4776066
C -4.4597593 1.0346499 -1.7002382
H -5.0297763 1.0118388 -2.6208419
C -3.1019954 0.7542510 -1.7274431
H -2.6288261 0.5027031 -2.6689059
$end
$rem
EXCHANGE LRC-wPBEPBE
OMEGA 260
BASIS 6-31G*
CIS_N_ROOTS 10
RPA 2
CIS_SINGLETS 1
CIS_TRIPLETS 0
CIS_DYNAMIC_MEM TRUE
CIS_RELAXED_DENSITY TRUE
USE_NEW_FUNCTIONAL TRUE
SOLVENT_METHOD PCM
PCM_PRINT 1
MAX_CIS_CYCLES = 200
$end
$pcm
NonEquilibrium
Theory IEFPCM
StateSpecific Peturb
$end
$solvent
Dielectric 35.688000 ! Acetonitrile
OpticalDielectric 1.806874
$end
which calculates excitation energies. The results from changing the solvent from AN to THF or water is within a nanometer for absorbance. Are we missing some parameter that means we aren’t properly taking solvent into account? Is there another method that is better at accounting for solvatochromism?
Additionally, there is the another parameter that you can feed into the non-eq PCM section which is ChargeSeperation = Excited. While there is an example that states that parameter should be used for emission, what is actually does is a little unclear. Could someone point me towards a resource that specifically reviews the parameters being used by QChem or give me some advice about the methods one has to use to incorporate non-eq solvent into TDDFT calculations to capture solvent effects first with absorbance energies and later with emission energies.
Thanks in advance!
(I couldn’t figure out to embed the output file into this question, but I am happy to provide more information)