Multiwfn forum

Dear Prof. Tian Lu,

First of all, thank you very much for your outstanding work on MULTIWFN and for managing the forum.

I am currently working on modeling π-π interactions between benzene dimers (Gaussian 16), for example in the “face-to-face” (FtF) geometry as shown in the attached figure. I performed the relaxed scan by keeping the monomer geometry fixed and  optimizing the distance between them. I think I made a mistake because in the route section I used:

opt=modredundant gen nosymm geom=connectivity counterpoise=2 blyp and mpiricaldispersion=gd3 int=grid=superfine

without including the frequency calculation. So, to “fix” the error, I was thinking of saving the minimum geometry obtained from the relaxed scan and calculating the vibrational frequencies based on that with the freq keyword. Is this the correct procedure in your opinion?

If I obtain negative vibrational frequencies, how should I proceed?

Thank you in advance,

Alessio

Dear Prof Tian Lu

First of all thank you so much for all your work of Multiwfn.

Actually, I'm working on modelling the π–π stacking between benzene dimers using the DFT (level of theory: 6-311+g(2d,2p) blyp empiricaldispersion=gd3), I would like to simply ask if there is any way in MULTIWFN to perfrom SAPT analysis on the optimized geometry?

I heard about the EDA energy decomposition analysis but I don't know the differences with SAPT.

Do you might have any suggestion ?

Thank you so much,
My best
Alessio

Dear Prof Tian Lu

First of all thank you so much for all your work of Multiwfn.

Actually, in collaboration with an experimental lab we are working on the dissociation reaction (retro michael reactions) of some thiols and some unsaturated aldehyde compounds such as crotonaldehyde. The experimental conditions are set at a temperature of 37° Celsius at pH 7.4 to study the dissociation reactions. I'm performing DFT calculations to support experiments.

I have a set of some thiolates molecule that I have optimized using the folowing level of theory:  'opt=calcfc freq=noraman wb97xd/6-311+g(d,p) scrf=(cpcm,solvent=water)', I have done the same also for TCE molecule as reference for calculate the nucleophilicity index.
I have used the implicit solvent and I have carried out the calculation of the nucleophilic index on the atttached thiolate (cysteamine) in the protonated form since the experiemental condition is pH 7.4 becuase we wanted to correlated kinetic constant as kon with nucleophilicity index so,

If possible, I have a couple of questions: 

1) Since I wanted to correlate with experimental data is right to include the implicit solvent in the calculation for the Nucleophilic index ? or  just considering the gas phase ?

2) Is it correct to calculate the nucleophilicity index considering the experimental conditions (for example considering the protonated amine NH3 since it's the same compund in the experiemntal lab), given that I want to compare it with experimental data? Is the nucleophilic index accurate for charged molecules ? or should I use another index?

Thank you so much,
My best
Alessio

Dear Prof Tian Lu,

First of all, thank you very much for your outstanding work on the Multiwfn software.

I have a question regarding bond order analysis. In the paper "Regio-selectivity prediction with a machine-learned reaction representation and on-the-fly quantum mechanical descriptors", the authors used the keyword pop=(full,mbs,hirshfeld,nbo6read) in Gaussian to extract NBO-based bond orders via the licensed NBO 6.0 program.

Is it possible to obtain similar bond order information from NBO population analysis using Multiwfn instead?

My best

Alessio

Dear Prof Tian Lu,

I'm wondering if I could ask you one question about the population analysis, because i'd like to obtain the partial charges.

Is the QTAIM very reliable respect to the NPA, Mulliken and NBO analysis ?
moreover considering one molecules and trying different population analysis methods, how to know whcih could be the best ?

Thank a lot

My best

Alessio Macorano

Dear Prof Tian Lu

Regarding to Electron density we are used to visualize them for a molecule, I would like to ask you how can I instead obtain a molecular descriptors to quantify the electron density, clearly I think that the total electron density cannot be quantified, but maybe in specific regions like HOMO and LUMO, yes.

Probably I miss to see the example in MULTIWFN.

Thank you for your work !!

Alessio

Dear Prof Tian Lu 

I would like to ask you one question about the topological surface analysis from .fchk of Gaussian or related QM software, the .fchk are generated from chk with b3lyp/6-311++g(d,p) with SMD implicit model solvent water.

On some drug like molecules i would like to use PSA (polar surface area) as molecular descriptors.

To do this i tried to calculate with multiwfn software from .fchk of Gaussian 16 software, but I obtain different values of PSA respect to Pubchem for example, and I don't understand why.

Maybe the difference is for the implicit model solvent ? should i have to consider in gas phase ?

Thank you so much for your work and this forum

Alessio