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#1 Re: Multiwfn and wavefunction analysis » Quantitative Molecular Surface Analysis recommended input file? » 2024-08-14 11:09:11
Tian,
This is really interesting. I also checked a citation in your paper wherein many molecules were screened for their charge separation or local polarity (PI-index) from Tore Brinck, Jane S. Murray & Peter Politzer.
They had CO2 in their dataset and actually got a large value for PI = 16.2 kcal/mol (my value from a very different DFT theory is close to 11.2 kcal/mol but close enough). They suspect this is because of high degree of charge separation in the molecule, which cannot be captured from dipole moment, just like you mentioned.
I look into what other descriptors can I extract from Multiwfn to see what correlates best with my experimental data.
Thank you once again 
Best regards,
Pranav
#2 Re: Multiwfn and wavefunction analysis » Quantitative Molecular Surface Analysis recommended input file? » 2024-08-14 08:46:47
Tian,
Thank you for your response. Makes sense.
I have two follow up questions:
1) So does it matter when optimizing geometry and generating .wfn on Guassian16, I do it in gas-phase (vacuum) or solvent-phase (SMD with water as the solvent)? I do these as two steps... First optimize and get .log file. Then I convert .log to .xyz, and feed that as an input to make .wfn. I keep DFT methods same for both steps.
I tried to compare my DFT method (gas- and solvent-phase) for 4 chemicals with published MPI from your work Carbon, 171, 514 (2021).
The values here are in kcal/mol
Chemical / Published (gas-phase) / MPI from Gas-phase / MPI from SMD water
cyclo[18]carbon / 2.6 / 2.45 / 2.46
ethane / 2.6 / 2.66 / 2.86
ethene / 6.7 / 6.86 / 7.55
benzene / 8.4 / 8.2 / 9.94
As observed, when optimizing and generating .wfn in a solvent-phase, MPI value increases. And my gas-phase numbers are comparable to your published values (good validation!)
2) I also ran the same process for a non-polar gas CO2. I am surprised as to why the MPI for CO2 is 11.19 kcal/mol... Because CO2 is regarded as a non-polar molecule. I checked my structure as it is linear as expected.
Regards,
Pranav
#3 Multiwfn and wavefunction analysis » Quantitative Molecular Surface Analysis recommended input file? » 2024-08-10 08:08:16
- pt007
- Replies: 4
Hi,
I am interested in extracting the ESP minima, maxima, and average value using the Quantitative Molecular Surface Analysis (option 12).
The molecules I work with are isolated ions. For example, 1-butyl-3-methylimidazolium, 1-butylpyridinium, etc. Each ion is a different file. I used DFT methods M06-2X/AUG-cc-pVTZ with SMD water solvent and GD3 correction (using Gaussian 16) to get the optimized structure of the ion. I can then output .log file (from which I can get optimized coordinated and make .xyz file) and .wfn file.
I have tried using the two different input files (.log/.xyz and .wfn) for Quantitative Molecular Surface Analysis and to no surprise, get different results for ESP descriptors.
What is the recommended input file for accurate calculations?
Some of my data correlates well with ESP average value using .log as input... When the same correlation is weak when .wfn input is used. I want to better understand why is that the case and which one should be considered more accurate.
Regards,
Pranav
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