If the system is too large to easily conduct a single point task at DFT level, an alternative choice is using xtb code (https://github.com/grimme-lab/xtb/) to perform the calculation via GFN-xTB theory (a semi-empirical DFT method), and let xtb to generate .molden file. Though the wavefunction quality of GFN-xTB theory is never as satisfactory as DFT, at least the corresponding .molden file can be normally analyzed by Multiwfn.

Here are the infos:

>> Which real space function did your analyzed in topology analysis module?
Electron density

>> How did you search the CPs (which commands you inputted?)
I am using the following sequence of commands:

2    <- Topological analysis
-1      <- Set CP searching parameters
1       <- Set maximal iterations:
2500
2       <- Set scale factor of stepsize
0.5
0
2    <- Search CPs from nuclear positions
3    <- Search CPs from midpoint of atom pairs
8    <- Generate the path connected (3,-3) and (3,-1)    #9    <- Generate the path connected (3,+1) and (3,+3)
-5    <- Modify or print detail or export paths, or calculate property along a path
1    <- Print summary of paths
4       <- Save points of all paths to paths.txt in current folder
6       <- Export paths as paths.pdb file in current folder
0       <- Return
0    <- Print and visualize all generated CPs, paths and surfaces
-4    <- Modify or export CPs (critical points)
-1    <- Print summary of CPs (in Angstrom)
4    <- Save CPs to CPs.txt in current folder
6    <- Export CPs as CPs.pdb file in current folder
0    <- Return
7       <- Show real space function values at specific CP or all CPs
0       <- If input 0, then properties of all CPs will be outputted to CPprop.txt in current folder
-10    <- Return

>> How did you generate your input file? What keywords were used in your quantum chemistry program?
I generate the input using GAUSSIAN.
The keywords were: #p scf=qc int=ultrafine output=wfn pm7
Here I put a zip with the input and output wavefunction and unformatted check file.

>> What is the chemical formula of your system?
My system is a boron-nitride nanotube with 4 cadmium atoms. The nanotubes ends were competed with hydrogens.

I found the following warning when searching for CPs:

Poincare-Hopf relationship verification:  164  -  232  +  101  -   14  =  19
Warning: Poincare-Hopf relationship is not satisfied, some CPs may be missing

How to improve the search?

I changed the maximal iterations to 2500 and the scale factor of stepsize to 0.5, but nothing changed.

Regards,

Camps