Multiwfn forum

In my opinion, if the CVB index is used to measure H-bond strength, "lowest value of the ELF for which all the core basins of the complex are separated from the valence" may not be the most reasonable way of defining ELF(C-V), because the role of donor atom and that of acceptor atom is very different in a H-bond, not only the hydrogen involved in the H-bond is bonded to the donor, but also ELF(DH-A) fully distinguishes donor and acceptor. Correspondingly, the ELF(C-V) should be an exclusive property of the donor side, and hence it is explicitly referred to as ELF(C-V,D) in the output of CVB index calculation function of Multiwfn.

Although the implementation of CVB index in Multiwfn is not exactly in line with the authors' original defintion for some systems, I think it is the most logically acceptable.

After performing topology analysis in Multiwfn, choose "-4 Modify or export CPs (critical points)" and then "6 Export CPs as CPs.pdb file in current folder". Also, after calculating grid data of Laplacian of rho in main function 5, export it as .cub file. After that, use VMD to show .cub file as an isosurface map, and show CPs.pdb as vdW style (with very small radius scale).

Dear Saeed,

Use main function 2 of Multiwfn to perform AIM topology as usual, then goto main function to calculate grid data of Laplacian of rho, then when you choose option -1 in the post-processing menu to visualize isosurface, and set bond radius to 0, you will find both BCPs and isosurfaces are shown.

Best regards,

Tian

The original SMD paper is sufficient

https://aapt.scitation.org/doi/10.1119/1.12937
https://aapt.scitation.org/doi/10.1119/1.13515

Please convert .gbw to .molden first via orca_2mkl, and manually check the .molden file via a text editor. If its format is not in line with the standard one, it is impossible to normally load it into Multiwfn. I believe the .gbw file produced by QM/XTB task doesn't contain any wavefunction information.

If you follows my steps mentioned earlier, you will be able to plot ELF for a specific spin. Just set occupation number of all beta orbitals to zero before plotting ELF in the regular way, you will obtain ELF-alpha map.

1 You can. PS: However, I strongly suggest using my code Molclus (http://www.keinsci.com/research/molclus.html) to perform conformation search, usually it is the best and most flexible choice.

2 Perhaps the reason is too many memory was assigned.

Dear Saeed,

Please check Section 4.4 of Multiwfn manual to understand how the actual plotting plane is defined in the main function 4 of Multiwfn.

Best regards,

Tian

There is unlikely a BCP. Topology analysis in AIM theory is unable to exhibit all kinds of interaction, as carefully discussed in my paper Chemistry—Methods 2021, 1, 231–239 https://doi.org/10.1002/cmtd.202100007
Even for a more evident intramolecular interaction, including nonnegligible intramolecular H-bonds, sometimes there is no corresponding BCP. The IRI method introduced in the above paper is able to exhibit much more interactions, and IRI analysis can be easily realized by Multiwfn.

In addition, the hyperconjugation interaction can be unveiled by NBO second-order perturbation analysis.

Please read "What should I do if some CPs of electron density were not successfully located?" in Section 4.2.1 of Multiwfn manual, this part lists all possible solutions. It is suggested to consider this scheme first:

It is frequently found that set scale factor of Newton step to 0.5-0.8 can greatly increase successful probability of finding the BCP corresponding to N-H bonds.

Thank you for your report. This piece of code should be changed to

		fragsurvar(:,2:3)=fragsurvar(:,2:3)/fragsurarea(:,2:3)
 		do ifrag=1,nsurfrag
			if (fragsurarea(ifrag,2)>0) fragsurvar(ifrag,1)=fragsurvar(ifrag,1)+fragsurvar(ifrag,2)
			if (fragsurarea(ifrag,3)>0) fragsurvar(ifrag,1)=fragsurvar(ifrag,1)+fragsurvar(ifrag,3)
 		end do

This issue will be fixed in the next update of Multiwfn.

I don't know what is "electron density surface"

If you want to obtain rdf of probability density of each orbital (i.e. norm of orbital wavefunction), it can be realized via Multiwfn (Please ensure that you are using the latest version of Multiwfn). In the interface of plotting rdf (i.e. subfunction 5 of main function 200), choose "1 Select real space function", then choose "44 Orbital probability density", then input the index of the orbital you are interested in. After that, you can choose option "0 Calculate radial distribution function and its integration curve" to calculate and visualize rdf.

If you are using ORCA, please use Multiwfn in combination with the .molden file generated by orca_2mkl instead of .wfx file.

Dear A. Escorcia,

If W employs pseudopotential, you need to manually modify .molden file via text editor to let Multiwfn know its actual effective nuclear charge, see Section 2.5 of Multiwfn manual (the paragraph beginning with "One severe drawback of Molden format is that it does not explicitly record nuclear charges..."). Alternatively, use the Multiwfn (updated no older than 2024-Sep-10) in combination with ORCA 6, because the molden file generated by ORCA 6 contains [pseudo] field, which can directly provide information of effective nuclear charges to Multiwfn.

If you have already taken care of above information, the result directly given by Multiwfn should be correct. If you still have doubts, please provide more information.

Best,

Tian