Multiwfn forum / Quantum Chemistry

CP2K GPAW method failed to converge with all electron basis

dummy@example.com (Hengyuan) — Thu, 30 Apr 2026 02:20:58 +0000

Here are the relevant input and output files
problem.zip

Frequency calculation in benzene dimer π–π stacking

dummy@example.com (alessiomacorano) — Tue, 14 Apr 2026 06:46:30 +0000

Dear Prof Tian Lu,

Thank you so much, this clears up the questions I had.

Thank you very much.

Alessio Macorano

Franc-Condon calculation error: low vibronic progression

dummy@example.com (sobereva) — Wed, 08 Apr 2026 20:21:42 +0000

This is an example of using redim=block, the first and second modes are ignored.

%oldchk=S0_optfreq.chk
#P freq(FCHT,readfc,readFCHT) geom=check

S0->S1 vibronic absorption

  0  1

reddim=block
Spectrum=HWHM=250

S1_optfreq.chk

1 2

Basis functions for 6-31G* used to fit SMD

dummy@example.com (sobereva) — Thu, 19 Mar 2026 19:16:17 +0000

Please only focused on how /auto affects relative energies, e.g. reaction energies and barriers. If this change is indeed significant, perhaps /auto in Gaussian is not well compatible with pseudopotential basis sets, it is suggested to use an all-electron basis set for TM instead and then check if the influence by /auto is in a reasonable range.

Advantages of (meta-)GGA functionals

dummy@example.com (sobereva) — Sun, 15 Mar 2026 20:56:48 +0000

Traditional pure functionals like PBE and TPSS nowdays have little value for calculating isolated systems, except for transition metal clusters. In addition, when PBE and TPSS are suitable for use, using r2SCAN instead is likely a better choice.

Basis set requirement for anions under very high level of theory

dummy@example.com (wham09) — Sun, 15 Mar 2026 16:31:48 +0000

I appreciate your replies!

FX175-ωPBE in orca

dummy@example.com (sid) — Tue, 10 Mar 2026 09:47:16 +0000

Dear members of the community,

I would like to get some information regarding how to perform a ΔUKS calculation with the FX175-ωPBE. I have checked the orca manual but I am bit confused with these functional as its not available in default. Could anyone help me with the input file format. I read that we have to provide the different amounts of Fock exchange (FX) and range-separation parameters. If someone one could shine some information regarding this it would be really helpful. I am trying to use this in Orca 6.1.1.

FYI: I am new to these type of tuning the functions.

Best regards
Sid

Judgement on DFT vs MR method selection

dummy@example.com (sobereva) — Wed, 04 Mar 2026 22:39:50 +0000

1 In most case DFT works reasonably. For example, H2+H• -> H• + H2, DFT can nicely represent the whole PES.

2 MRPT is not absolutely necessary, depending on the specific reaction.

3 If transition metal is directly involved in the process, multireference treatment may be necessary, but still not always.

4 When excited state is involved, the situation is significantly more complex; whenever possible, using a proper multireference method is recommended, especially when transition metal participates in the process.

Applying Marcus theory by QM calculation

dummy@example.com (wham09) — Wed, 04 Mar 2026 10:08:49 +0000

Dear Prof. Lu,

I would like to apply semi-classical Marcus model to evaluate solution-state electron transfer rate constants, for which I have multiple questions.

1. Let's say the ET reaction is A + B -> A(+) + B(-). In principle, should I calculate two sets of driving forces (delta_G), Huang-Rhys factors (S), the corresponding frequencies (omega), and reorganization energies (lambda) from separate calculations of A, A(+), B, B(-), and then combine them somehow?
Or should I optimize the geometry of A...B bimolecular complex, and then optimize A(+)...B(-) complex by TD optimization (following the CT state) and finally calculate one set of the factors?

2. In your blog post (sobereva.com/330), you stated that lambda_outer is difficult to calculate and often approximated. But in another post (sobereva.com/333), you presented quite clearly how to calculate it. Is the method presented in the article 333 indeed the standard way? Or is the accuracy of this approach questionable?

3. From your lecture notes and blog posts, I think I have some understanding of how to calculate all the terms required in the semi-classical Marcus equation, except the electronic coupling (NAC or H_ab). Is it correct that the most rigorous way to get this is to optimize the MECP geometry of the A…B complex, at which the intermolecular electron transfer actually happens, and then obtain the eigenvalue difference?
If there is other way that is more standard or commonly used, can it be done using Gaussian or ORCA?

4. If I wanted to calculate rate of outer-sphere electron transfer between an organic reactant and an electrode (in a solution of electrolyte in organic solvent), I could imagine that there will be many more uncertainties, such as:
1) how to optimize the distance between the electrode and the reactant at the moment of ET, and how to simulate the double layer environment at this distance
2) how to optimize geometry of the reactant in the presence of electric field, organic solvent, and electrolyte
3) how to calculate the terms in the Marcus equation when electrode is involved
About this question, I'm basically a novice. Can all these be addressed by QM methods (desirably using Gaussian or ORCA)? If not, is there a less rigorous, but good enough QM routine that researchers use?

Weird Explosion of atoms in IRC

dummy@example.com (hehe) — Fri, 20 Feb 2026 11:51:01 +0000

Hi Tian lu,

Thanks for the reply. Honestly, im unaware but i just decided to take the geometry and redo downhill and it worked fine. I reckon it is some issue when using chk to read the geometry which worked fine in the initial stages but for some reason, fails in this particular restart. "Restarting" completely with geometry written (without geom=allcheck) worked as expected

I do have a followup question:
I am not entirely aware of the algorithm but is there a difference in optimising when you are somewhat close to local minimum vs using downhill....?

Thanks,
hehe

Reorganization energy and Huang-Rhys factor from ORCA 6.1.1 ESD module

dummy@example.com (sobereva) — Fri, 06 Feb 2026 19:53:20 +0000

In principle, evaluation of reorganization energies and H–R factors do not need NACME.
NACME is used by ORCA_ESD when evaluating internal conversion rate.

Solvent participation after transition state

dummy@example.com (sobereva) — Tue, 03 Feb 2026 23:49:00 +0000

I seems that the elemenary step of generating D-THF is missing in the energy profile map. There should be a weakly interacting complex like TS'...THF, which corresponds to a PES minimum, and the TS' is the (unstable) molecule produced after passing through TS. THF will react with TS' to yield D-THF. Only when the complete reaction profile is constructed, the reaction rate can be estimated.

Adjusting halogen radius for geometry optimization

dummy@example.com (sobereva) — Sun, 01 Feb 2026 23:31:07 +0000

The change of the radius doesn't necessarily improve geometry optimization convergence for systems containing Br atom, but as it solved your problem, it is acceptable. Using the SMD18 radius, even for PBE0, should be generally better (in the accuracy of energy aspect) than the original SMD radius.

S1 optimization with negative frequency

dummy@example.com (sobereva) — Thu, 29 Jan 2026 18:45:56 +0000

I suggest using tigher SCF and opt thresholds, and slightly adjusting structure along imaginary mode, and then retry. Try you best to eliminate any imaginary frequency. (However, if you make sure that those groups have little impact on the result of your interest, you may simply replace them by hydrogen atoms...)

Native B3LYP vs LibXC(B3LYP) for S₀ and S₁ optimizations in ORCA (ESD

dummy@example.com (Arivu) — Wed, 21 Jan 2026 07:43:07 +0000

Thank you so much for the clarifications Prof. Tian Lu.