Multiwfn forum

prasanta13

Member

Registered: 2018-12-30

Posts: 39

ESP generation

Hello Dr Tian Lu
I am posting few issues relating to the generation of Vsmax.
I have optimized few molecules with RI-MP2/aug-cc-pvtz in ORCA 4.2.1 and generated .wfn and .wfx files. I loaded those files with Multiwfn and went to option 12 to 12 (Quantitative analysis of Molecular surface) and start analysis. I have Gaussian configured with Multiwfn but the Multiwfn generates the surface in its own engine. The results obtained are ridiculous. The reported Vs,max of the same region of the same molecule (F2) is 14, whereas Multiwfn shows it 53 kcal/mol.
So, where the problem is?
a. The ORCA wfn files can not be used?
b. Only the gaussian fchk files to be used?
c. The cubegen can work with only fchk files but not of wfn/wfx files?
d. What is the cause of this error in Vsmax value.

Thanking You.

sobereva

Tian Lu (Multiwfn developer)

From: Beijing

Registered: 2017-09-11

Posts: 1,775

Website

Re: ESP generation

a) ORCA wfn/wfx file can be normally used, however, in this case you cannot utilize cubegen to significantly accelerate ESP calculation as .fch/fchk file, since cubegen can only read fch/fchk file.

b) No. Any supported format that contain GTF information can be employed as input file for this kind of analysis, such as .mwfn, .gms, .molden. See Section 2.5 of Multiwfn manual for description.

c) Right. However, if your code (such as ORCA) can produce molden file, you can use subfunction 2 of main function 100 to convert the molden file to fch file, then if use the fch file as input file, you can normally let Multiwfn utilize cubegen to calculate ESP.

d) I cannot give you definitive answer without having your ORCA input file and .wfn/wfx file. You can upload them to a netdisk, I will check.

It is important to notice that if you employ ORCA to carry out MP2 calculation, by default the exported wfn/wfx file only contains HF orbitals, evidently the analysis accuracy will be quite poor. Without special reasons, I strongly suggest using normal DFT functional instead, such as B3LYP, PBE0, wB97X-D3... If you really want to study ESP at MP2 level, you have to ask ORCA to generate natural orbitals at MP2 level, additional cost will be needed.

For an ORCA user, if Gaussian is available and the system to be studied is not small, my general recommendation of ESP analysis is using ORCA to perform optimization at DFT level (not double-hybrid functional), then convert the resulting gbw file to molden file (see beginning of Chapter 4 of Multiwfn manual on how to do), then convert molden file to fch file (as mentioned above), then use the fch file as input file to perform quantitative surface analysis of ESP.