Dear all:
I’m working on a project where I use ESP charges from ground and excited states. I’ve encountered a confusion when using TDDFT (with CAM-B3LYP) for analyzing ground-state charges — yes, I know TDDFT is intended for excited states, but I’ll explain why I’m asking.
My system consists of a polymer of 122 atoms, and I need two set of charges:
- DFT-ESP ground state charges.
- TDDFT - ESP excited state charges.
However, when I get the results from DFT, I get odd charges, like -17 for a carbon atom, and then another carbon atom of 16. Then, when I compute the charges for the excited state using the next input:
BASIS = 6-31+G*
CIS_CONVERGENCE = 6
CIS_N_ROOTS = 5
CIS_TRIPLETS = FALSE
CIS_RELAXED_DENSITY = TRUE
RPA = 0
GUI = 2
ESP_CHARGES = 1
METHOD = CAMB3LYP
One I had the output from the TDDFT, I realized that it also included a list of ground state ESP charges before the set of charges for excited states, and those didn’t match at all with the DFT ESP charges. In fact, those from the TDDFT calculation made more sense than DFT.
I then compared the approach by getting the same set of charges for a smaller molecule, and this time, the charges in ground state from DFT and TDDFT matched exactly.
Has anyone worked with this kind of set up before? Do you know why this might be happening?
Thanks for your help,
Samantha.
can you provide an example with a complete input file?
This is for TDDFT:
$molecule
0 1
S 140.30000 113.33000 37.69000
C 141.14000 112.90000 39.14000
C 140.70000 113.73000 40.15000
C 139.70000 114.68001 39.77000
H 139.32001 115.43000 40.45000
C 139.35001 114.56001 38.46000
H 138.49001 114.91000 37.90000
C 141.17000 113.67000 41.57000
S 143.35001 111.37000 40.00000
C 143.92000 110.08000 38.99000
C 143.11999 109.95000 37.88000
C 142.06000 110.90000 37.89000
H 141.39000 110.93001 37.04000
C 142.00000 111.74000 38.97000
C 143.29001 108.97000 36.76000
S 146.00000 108.37000 38.27000
C 147.14000 107.83000 39.46000
C 146.76000 108.27000 40.70000
C 145.64000 109.14000 40.65000
H 145.17999 109.56001 41.53000
C 145.08000 109.30000 39.41000
C 147.51001 108.10001 41.98000
S 149.39000 106.14999 39.97000
C 150.36999 105.74001 38.59000
C 149.95000 106.31000 37.42000
C 148.86999 107.19000 37.74000
H 148.49001 107.85000 36.97000
C 148.35001 107.15000 39.00000
C 150.42000 106.19000 36.00000
S 152.93001 104.84000 38.11000
C 153.44000 103.45001 39.02000
C 152.50000 103.02000 39.93000
C 151.32001 103.81000 39.90000
H 150.48001 103.74000 40.58000
C 151.42000 104.79000 38.95000
C 152.59000 101.94000 40.97000
S 155.63001 101.91000 39.75000
C 156.73999 101.28999 38.57000
C 156.39000 101.82000 37.35000
C 155.23000 102.65000 37.37000
H 154.81000 103.11000 36.48000
C 154.61000 102.69000 38.59000
S 158.39999 99.18000 37.89000
C 159.55000 98.59000 39.06000
C 159.42000 99.20000 40.28000
C 158.39000 100.17999 40.20000
H 158.16000 100.81001 41.06000
C 157.77000 100.35000 39.00000
C 160.27000 99.00000 41.50000
S 161.95000 97.08000 39.48000
C 162.36000 95.81001 38.36000
C 161.39999 95.80000 37.39000
C 160.38001 96.79000 37.53000
H 159.55000 96.88000 36.84000
C 160.51001 97.56000 38.65000
C 161.26000 94.85000 36.23000
S 164.31000 93.92000 37.56000
C 165.34000 93.06000 38.65000
C 165.00000 93.53000 39.90000
C 164.06000 94.60000 39.89000
H 163.86000 94.99000 40.88000
C 163.44000 94.89000 38.70000
C 165.45000 93.09000 41.26000
S 167.49001 91.42999 39.25000
C 168.16000 90.45999 37.98000
C 167.57999 90.78000 36.77000
C 166.53000 91.73000 36.86000
H 165.98000 92.20001 36.06000
C 166.39000 92.19000 38.15000
C 167.85001 90.17000 35.42000
S 170.55000 89.26000 37.17000
C 171.45001 88.25000 38.25000
C 170.67000 88.01000 39.36000
C 169.48000 88.78999 39.40000
H 168.69000 88.72000 40.13000
C 169.23999 89.52000 38.27000
C 171.01000 87.02000 40.44000
S 173.65999 86.42000 38.24000
C 175.06000 86.84000 37.29000
H 175.91000 86.18000 37.24000
C 174.95001 88.13000 36.83000
C 173.67999 88.67000 37.17000
H 173.29001 89.65000 36.91000
C 172.78999 87.86000 37.83000
C 175.89999 88.94000 35.99000
H 175.48689 89.91260 35.82177
H 176.05253 88.45000 35.05110
H 176.83609 89.03340 36.49980
H 167.23313 90.64331 34.68492
H 167.62902 89.12352 35.45082
H 168.87974 90.30972 35.16499
H 166.15039 92.28710 41.16149
H 164.60437 92.75827 41.82548
H 165.91654 93.91045 41.76408
H 160.39830 95.11522 35.65377
H 161.14935 93.85143 36.59813
H 162.13285 94.90832 35.61387
H 160.97021 98.21088 41.32139
H 159.64667 98.74251 42.33069
H 160.79934 99.90398 41.71800
C 157.14000 101.59000 36.08000
H 156.65818 102.11425 35.28130
H 157.15687 100.54292 35.86037
H 158.14254 101.94798 36.18800
H 149.81600 106.80984 35.37081
H 150.33802 105.17164 35.68202
H 151.44112 106.50296 35.93462
H 171.94247 86.54806 40.21053
H 170.24040 86.27901 40.49974
H 171.08899 87.52861 41.37807
H 153.52597 101.43030 40.87481
H 151.78916 101.24400 40.83165
H 152.51897 102.37635 41.94440
H 148.31658 107.41262 41.83219
H 146.85059 107.71975 42.73198
H 147.90028 109.04584 42.29302
H 141.91320 112.90646 41.66774
H 140.34251 113.44636 42.21043
H 141.59023 114.61429 41.84681
H 142.51090 109.11202 36.04047
H 143.24064 107.97375 37.14722
H 144.23993 109.12420 36.29226
$end
$rem
BASIS = 6-31+G*
CIS_CONVERGENCE = 6
CIS_N_ROOTS = 20
CIS_TRIPLETS = FALSE
CIS_RELAXED_DENSITY = TRUE
RPA = 0
GUI = 2
ESP_CHARGES = 1
METHOD = CAMB3LYP
MEM_STATIC = 3000
MEM_TOTAL = 180000
$end
This is for DFT:
$molecule
0 1
S 140.30000 113.33000 37.69000
C 141.14000 112.90000 39.14000
C 140.70000 113.73000 40.15000
C 139.70000 114.68001 39.77000
H 139.32001 115.43000 40.45000
C 139.35001 114.56001 38.46000
H 138.49001 114.91000 37.90000
C 141.17000 113.67000 41.57000
S 143.35001 111.37000 40.00000
C 143.92000 110.08000 38.99000
C 143.11999 109.95000 37.88000
C 142.06000 110.90000 37.89000
H 141.39000 110.93001 37.04000
C 142.00000 111.74000 38.97000
C 143.29001 108.97000 36.76000
S 146.00000 108.37000 38.27000
C 147.14000 107.83000 39.46000
C 146.76000 108.27000 40.70000
C 145.64000 109.14000 40.65000
H 145.17999 109.56001 41.53000
C 145.08000 109.30000 39.41000
C 147.51001 108.10001 41.98000
S 149.39000 106.14999 39.97000
C 150.36999 105.74001 38.59000
C 149.95000 106.31000 37.42000
C 148.86999 107.19000 37.74000
H 148.49001 107.85000 36.97000
C 148.35001 107.15000 39.00000
C 150.42000 106.19000 36.00000
S 152.93001 104.84000 38.11000
C 153.44000 103.45001 39.02000
C 152.50000 103.02000 39.93000
C 151.32001 103.81000 39.90000
H 150.48001 103.74000 40.58000
C 151.42000 104.79000 38.95000
C 152.59000 101.94000 40.97000
S 155.63001 101.91000 39.75000
C 156.73999 101.28999 38.57000
C 156.39000 101.82000 37.35000
C 155.23000 102.65000 37.37000
H 154.81000 103.11000 36.48000
C 154.61000 102.69000 38.59000
S 158.39999 99.18000 37.89000
C 159.55000 98.59000 39.06000
C 159.42000 99.20000 40.28000
C 158.39000 100.17999 40.20000
H 158.16000 100.81001 41.06000
C 157.77000 100.35000 39.00000
C 160.27000 99.00000 41.50000
S 161.95000 97.08000 39.48000
C 162.36000 95.81001 38.36000
C 161.39999 95.80000 37.39000
C 160.38001 96.79000 37.53000
H 159.55000 96.88000 36.84000
C 160.51001 97.56000 38.65000
C 161.26000 94.85000 36.23000
S 164.31000 93.92000 37.56000
C 165.34000 93.06000 38.65000
C 165.00000 93.53000 39.90000
C 164.06000 94.60000 39.89000
H 163.86000 94.99000 40.88000
C 163.44000 94.89000 38.70000
C 165.45000 93.09000 41.26000
S 167.49001 91.42999 39.25000
C 168.16000 90.45999 37.98000
C 167.57999 90.78000 36.77000
C 166.53000 91.73000 36.86000
H 165.98000 92.20001 36.06000
C 166.39000 92.19000 38.15000
C 167.85001 90.17000 35.42000
S 170.55000 89.26000 37.17000
C 171.45001 88.25000 38.25000
C 170.67000 88.01000 39.36000
C 169.48000 88.78999 39.40000
H 168.69000 88.72000 40.13000
C 169.23999 89.52000 38.27000
C 171.01000 87.02000 40.44000
S 173.65999 86.42000 38.24000
C 175.06000 86.84000 37.29000
H 175.91000 86.18000 37.24000
C 174.95001 88.13000 36.83000
C 173.67999 88.67000 37.17000
H 173.29001 89.65000 36.91000
C 172.78999 87.86000 37.83000
C 175.89999 88.94000 35.99000
H 175.48689 89.91260 35.82177
H 176.05253 88.45000 35.05110
H 176.83609 89.03340 36.49980
H 167.23313 90.64331 34.68492
H 167.62902 89.12352 35.45082
H 168.87974 90.30972 35.16499
H 166.15039 92.28710 41.16149
H 164.60437 92.75827 41.82548
H 165.91654 93.91045 41.76408
H 160.39830 95.11522 35.65377
H 161.14935 93.85143 36.59813
H 162.13285 94.90832 35.61387
H 160.97021 98.21088 41.32139
H 159.64667 98.74251 42.33069
H 160.79934 99.90398 41.71800
C 157.14000 101.59000 36.08000
H 156.65818 102.11425 35.28130
H 157.15687 100.54292 35.86037
H 158.14254 101.94798 36.18800
H 149.81600 106.80984 35.37081
H 150.33802 105.17164 35.68202
H 151.44112 106.50296 35.93462
H 171.94247 86.54806 40.21053
H 170.24040 86.27901 40.49974
H 171.08899 87.52861 41.37807
H 153.52597 101.43030 40.87481
H 151.78916 101.24400 40.83165
H 152.51897 102.37635 41.94440
H 148.31658 107.41262 41.83219
H 146.85059 107.71975 42.73198
H 147.90028 109.04584 42.29302
H 141.91320 112.90646 41.66774
H 140.34251 113.44636 42.21043
H 141.59023 114.61429 41.84681
H 142.51090 109.11202 36.04047
H 143.24064 107.97375 37.14722
H 144.23993 109.12420 36.29226
$end
$rem
BASIS = 6-31+G*
GUI = 2
ESP_CHARGES = 1
METHOD = CAMB3LYP
MEM_STATIC = 3000
MEM_TOTAL = 180000
$end
I will run these and see what I can discover. One immediate thought, however, is that for medium-size molecules with diffuse functions, you need to set the thresholds tighter. In your output file for DFT, you should see the following warning:
Overlap eigenvalue is smaller than square root of threshold
Use THRESH >= 12 to get rid of this warning
Linear dependence detected in AO basis
Tighter screening thresholds may be required for diffuse basis sets
Use S2THRESH > 14 and THRESH = 14 in case of SCF convergence issues
You should take this seriously and adjust THRESH and S2THRESH as indicated. I can already see that this is adversely affecting SCF convergence for the DFT job, where the default THRESH = 9 whereas for TD-DFT it defaults to THRESH = 12 and convergence is much faster because there is less issue with numerical linear dependencies. See this paper for a discussion of how tightening the thresholds actually makes the calculations faster.
https://doi.org/10.1021/acs.jpca.4c00283
I believe that Q-Chem v. 6.3 may adjust this in a more automated way, to help with SCF convergence robustness. However, in general users need to pay attention to the messages in the output file - often there’s important information there.
Update: even in the ground-state calculation, the anomalous Merz-Kollman charges go away if you tighten up the thresholds. (S2THRESH=16 and THRESH = 12 will work, which is my go-to combination for medium-size molecules with diffuse functions.) Please pay attention to warning messages that Q-Chem prints out, they are trying to tell you something.
Selecting SCF_CONVERGENCE = 8 will automatically put THRESH = 12, which is where the difference between ground-state and TDDFT is coming from. (You could get the same effect in the ground state by setting SCF_CONVERGENCE = 8 manually.) In general you should use SCF_CONVERGENCE = 8 for computing properties.
Thank you so much!
I tried for one of my molecules and it worked! I’ll follow your advice, currently I’m reading more about that warning because I’m still a bit unfamiliar with it, thanks again for the time and for doing the calculations yourself.
Best,
Samantha