Thanks a lot.

For simulating UV-Vis purpose, neither IOp(9/40=x) nor Population=Full affects result. Only for most electron excitation analyses in Multiwfn, IOp(9/40=4) (at least =3) should be added.

Best,

Tian

Thanks a lot. All the questions have been answered very well and quickly which is very much appreciable. Thanks.

However, Just for my curiosity, I have been reading to increase the precision of UV-vis while performing calculation using Internal Operation (Iops), which is suggested by different by different sources. So, going through different resouces, I am a bit confused which one to use.

1- From books of  Exploring Chemistry with Electronic Structure Methods, Third Edition
by James B. Foresman at chapter-8, page-334.

"Running the excited state calculation with the Population=Full and IOp(9/40=3) keywords makes this process easier. These keywords request that all molecular orbitals (occupied and virtual) be included in the population analysis and that all function coefficients greater than 0.001 be included in the excited state output (the default cutoff is 0.1), respectively."

2- From Gaussum website (https://gausssum.sourceforge.net/GaussS … index.html),

"I wanted to calculate the UV-Vis absorption spectrum of divinylbenzene. I added the keyword IOP(9/40=2) to the TD-DFT command, to output information on smaller contributions to each electronic transition."

3- From your incredible useful multiwfn manual:

"Gaussian users: Output file (.out or .log) of CIS, TDHF, TDDFT and TDA-DFT tasks can be used. Both single point and optimization tasks are supported; for the latter case, Multiwfn analyzes electronic excitation at the final geometry. Since by default Gaussian only outputs the configuration coefficients whose absolute value is larger than 0.1, In order to achieve acceptable accuracy, you must add IOp(9/40=4) keyword in the route section so that all configuration coefficients whose magnitude larger than 0.0001 will be printed (If the calculation in Multiwfn is found to be too expensive, using IOp(9/40=3) instead is also generally acceptable). Implicit solvation model, including external iteration (state specific) treatment of solvent response to transition, is fully compatible."

So, My question is which one is more precise? If each of them is correct, which one is more precise. How to know using IOps manual (available on Gaussian16 website [https://gaussian.com/overlay9/#iop_(9/40)])?

Thanks
Mukesh Singh

Note that for TD case, there are not only excitations but also deexcitations, the latter has negative contribution.

Q2: Multiwfn manual is quite detailed. See "2 Basic knowledge about single-reference methods" in Section 3.21.A of Multiwfn manual for relevant information.

Q3: You can directly read coefficients from output file of quantum chemistry code.

Thanks a lot for quick reply and indicating to improve the precision of my calculations. I have used the following tag for calculations.

-------------------------
%mem=2GB
%nprocshared=8
%oldchk=DHQ_new_H_uv.chk
%chk=DHQ_new_H_uv.chk
# td=(nstates=40)IOp(9/40=4) b3lyp/6-31g(d,p) pop=full geom=connectivity

DHQ_new_H_uv

0 1
C                  0.00000700   -1.95763800   -4.06463700
C                 -0.15740800    2.48981100   -0.68715700
C                  0.07016400   -2.00137200    2.69367800
C                 -0.07016800    2.00137200   -2.69367900
C                  0.15740800   -2.48981100    0.68715800
C                  0.00000000    1.95763700    4.06463600
C                 -0.00000700    1.95763800   -4.06463700
C                  0.15740800   -2.48981100   -0.68715700
C                 -0.07016400    2.00137200    2.69367800
C                  0.07016800   -2.00137200   -2.69367900
C                 -0.15740800    2.48981100    0.68715800
C                  0.00000000   -1.95763700    4.06463600
C                  0.17089600   -3.23790700   -1.99024400
C                 -0.06950700    1.25549300    1.38097900
C                  0.05278300   -3.21106900    4.73440300
C                 -0.05279200    3.21107000   -4.73440300
C                  0.06950800   -1.25549300   -1.38098000
C                 -0.17089400    3.23790700    1.99024400
C                 -0.17089600    3.23790700   -1.99024400
C                  0.06950700   -1.25549300    1.38097900
C                 -0.05278300    3.21106900    4.73440300
C                  0.05279200   -3.21107000   -4.73440300
C                 -0.06950800    1.25549300   -1.38098000
C                  0.17089400   -3.23790700    1.99024400
C                  0.22043900   -4.45147100   -2.62360600
C                 -0.22043900    4.45147100   -2.62360600
C                  0.00000000    0.00000000    0.75670900
C                  0.16154700   -4.41009800    4.04468500
C                 -0.16154700    4.41009800    4.04468500
C                  0.16155400   -4.41009900   -4.04468400
C                 -0.16155400    4.41009900   -4.04468400
C                  0.00000000    0.00000000   -0.75670900
C                  0.22043500   -4.45147000    2.62360600
C                 -0.22043500    4.45147000    2.62360600
H                 -0.00441900    3.22694800    5.81928400
H                 -0.19842000    5.34161700    4.60162200
H                 -0.29540100    5.39677200    2.09556200
H                 -0.10259400   -1.03928700    4.63088800
H                  0.00441900   -3.22694800    5.81928400
H                  0.19842000   -5.34161700    4.60162200
H                  0.29540100   -5.39677200    2.09556200
H                  0.10259400    1.03928700    4.63088800
H                 -0.29540500    5.39677200   -2.09556100
H                 -0.19842800    5.34161800   -4.60162200
H                 -0.00443000    3.22694900   -5.81928500
H                  0.10258500    1.03928700   -4.63089000
H                 -0.10258500   -1.03928700   -4.63089000
H                  0.00443000   -3.22694900   -5.81928500
H                  0.19842800   -5.34161800   -4.60162200
H                  0.29540500   -5.39677200   -2.09556100

1 10 2.0 22 1.5 47 1.0
2 11 2.0 19 1.0 23 1.5
3 12 2.0 20 1.0 24 1.5
4 7 2.0 19 1.5 23 1.0
5 8 2.0 20 1.5 24 1.0
6 9 2.0 21 1.5 42 1.0
7 16 1.5 46 1.0
8 13 1.0 17 1.5
9 14 1.0 18 1.5
10 13 1.5 17 1.0
11 14 1.5 18 1.0
12 15 1.5 38 1.0
13 25 2.0
14 27 1.5
15 28 1.5 39 1.0
16 31 1.5 45 1.0
17 32 1.5
18 34 2.0
19 26 2.0
20 27 1.5
21 29 1.5 35 1.0
22 30 1.5 48 1.0
23 32 1.5
24 33 2.0
25 30 1.5 50 1.0
26 31 1.5 43 1.0
27 32 1.0
28 33 1.5 40 1.0
29 34 1.5 36 1.0
30 49 1.0
31 44 1.0
32
33 41 1.0
34 37 1.0
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50

--------------------------

Its log file includes much larger number of transition in each exictated states. However, the transition % as calculated here by Multiwfn remains same:

#   1   1.4060 eV    881.82 nm   f=  0.06970   Spin multiplicity= 1:
   H -> L 100.5%
#   2   2.2645 eV    547.51 nm   f=  0.09090   Spin multiplicity= 1:
   H -> L+1 82.1%, H-1 -> L 16.2%
#   3   2.6079 eV    475.42 nm   f=  0.08240   Spin multiplicity= 1:
   H-1 -> L 81.6%, H -> L+1 14.9%

Now,

Q. Any suggestion to improve it?

Q. what formulae are being used to calculate transition probability in multiwfn? Does the formula differ for restricted/unrestricted/default (option chosen from gv6)? Any references will be appreciable.

Q. Is there any way to write directly the coefficient instead of writing the transition % using Multiwfn. If it can be done using some bash/python-scripting, please let me know, I will to do it?

thanks
Mukesh Singh

You should add keyword IOp(9/40=4), as mentioned in the "Input files" part of Section 3.21.A of Multiwfn manual, otherwise analysis result may be evidently inaccurate.

Best,

Tian

I am performing a uv-vis calculation of a 2D quantum dot. Which has even number of electrons and passivated by hydrogen atom.

So, after calculating the UV-vis, I calculated the transition probablity using multiwfn code, I am getting transition probability ~100.5%.

And on passivating with halogens (F, Cl and Br), I am getting the transition probability 100.6, 100.9 and 101%.   

Further, I check their coefficient for confirmation. My calculated transition probability seems to be consistent with calculation of Multiwfn.

eg.

Excited State   1:      Singlet-A      1.4060 eV  881.83 nm  f=0.0697  <S**2>=0.000
     110 ->111         0.70886
     110 <-111        -0.10122

So, probality should be 2*np.array([0.70886, -0.10122])**2*100= array([100.49649992,   2.04909768]).

Hence first transition probability is 100.5%.

Now my question, what are possible reasons of turning out transition probability more than 100%?

Have any body found similar things before?

If yes of any of these question, could be you please share your suggestion? And any related paper would be greatly appreciable.

Thanks
Mukesh Singh
IIT Bombay.