Sincerely,
Saeed

CRUCIAL_explanations2.pdf

Sincerely yours,
Saeed

1 delta-SCF itself is an iterative process, reaction field is intrinsically updated during the SCF iteration, so external iteration is never needed for consideration of solvent effect.

2 ORCA doesn't have this feature, this is one of evident limitations of ORCA (especially for studying CT excitation in solvent environment as linear response model performs poorly in this case). The corrected linear-response model that available in G16 is also not supported by ORCA.

I suggest checking what is the nature of the low-energy transitions (>1000 nm) using hole-electron analysis in Multiwfn, which can provide valuable physical insight.

Also, don't forget to confirm that the reference state wavefunction is stable.

Thank you for the information, but I need the magnetic dipole moments also, can i get it from ORCA ? if yes please tell me how to get it.

Example:

------------------------------------------------------------------------------------------
                     CD SPECTRUM VIA TRANSITION ELECTRIC DIPOLE MOMENTS    
------------------------------------------------------------------------------------------
     Transition      Energy     Energy  Wavelength    R        MX        MY        MZ   
                      (eV)      (cm-1)    (nm)   (1e40*cgs)   (au)      (au)      (au)  
------------------------------------------------------------------------------------------
  0-1A  ->  1-1A    3.332995   26882.4   372.0    2.25885   0.02004   0.00002  -0.18886
...

MX MY MZ are components of transition magnetic dipole moment.

Some settings in your file are not reasonable or redundant. For example, ALPHA 0.01, is too aggressive. The settings to tune GAPW calculations are not necessary. Importantly, the cell is very small, and Pt slab it a conductor, considering k-point sampling is indispensable.

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

Thank you very much.

Alessio Macorano

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

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.

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?