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Re: Reduce cost of ESP analysis on molecular surface for ORCA users

dummy@example.com (sobereva) — Tue, 19 Jan 2021 20:57:12 +0000

When Multiwfn asks you to select grid, please choose "8 Use grid setting of another cube file", then input path of another grid file, then the current calculation will employ exactly the same grid setting as another cube file.

Re: Reduce cost of ESP analysis on molecular surface for ORCA users

dummy@example.com (michaelp) — Tue, 19 Jan 2021 08:00:40 +0000

Thank you for this post. It is indeed a much faster way to get the MEP. I have a problem though with the grid definition. I would like to visualise the ELF and colour-code it with the MEP. In order to do this I generate an ELF cube and I copied the spacing of the grid points from that calculation. I then follow your scheme, but I change the spacing to exactly the same value as used for the ELF cube. Still, the final MEP cube has different dimensions and can therefore not be used to colour code the ELF cube. Is there any way to lift this problem?

Kind regards,
Michael

Re: Reduce cost of ESP analysis on molecular surface for ORCA users

dummy@example.com (sobereva) — Fri, 08 Jan 2021 19:39:03 +0000

fjbenitez wrote:

Hi!
I tried to use your suggestion and the program says the following: "Note: Albeit "orca_2mklpath" parameter in settings.ini has been defined, the orca_2mkl executable file cannot be located, therefore the .gbw file cannot be directly opened by Multiwfn".
So, what do I do?
PS: I'm new at this, just trying it for the first time

Multiwfn cannot directly open .gbw file because it is a private binary format of ORCA. If you want to directly use .gbw file as input file of Multiwfn without manually converting it to .molden file, which is supported by Multiwfn, you should define "orca_2mklpath" in settings.ini to actual path of orca_2mkl executable file in ORCA folder, in this case Multiwfn will automatically invoking orca_2mkl to convert .gbw to .molden when Multiwfn loads .gbw file.

Re: Reduce cost of ESP analysis on molecular surface for ORCA users

dummy@example.com (fjbenitez) — Thu, 07 Jan 2021 21:48:38 +0000

Hi!
I tried to use your suggestion and the program says the following: "Note: Albeit "orca_2mklpath" parameter in settings.ini has been defined, the orca_2mkl executable file cannot be located, therefore the .gbw file cannot be directly opened by Multiwfn".

So, what do I do?

PS: I'm new at this, just trying it for the first time

Re: Reduce cost of ESP analysis on molecular surface for ORCA users

dummy@example.com (sobereva) — Mon, 09 Mar 2020 22:23:25 +0000

In the post-process menu of main function 12, you can only choose to export ESP at surface vertices (the option 12 is used to export the grid data used for defining surface, namely electron density grid data).

Re: Reduce cost of ESP analysis on molecular surface for ORCA users

dummy@example.com (jimkress) — Mon, 09 Mar 2020 21:31:06 +0000

Thanks again for the suggestion. It appears to work OK.

When I choose to export the cube file, does it export the ESP values at all the points or just the ones in the surface being displayed?

Thanks.

Jim

Re: Reduce cost of ESP analysis on molecular surface for ORCA users

dummy@example.com (sobereva) — Sat, 07 Mar 2020 02:56:24 +0000

If you want to use MP2 density to analyze ESP on molecular surface, you should use following procedure

Example input file:

! mp2 def2-SVP keepdens
%mp2
density relaxed
natorbs true
end
* xyz   0   1
O     -0.00000000   -0.00000000    0.11930801
H      0.00000000    0.75895306   -0.47723204
H     -0.00000000   -0.75895306   -0.47723204
 *

After calculation, you will have h2o.mp2nat and h2o.pmp2re in current folder, the former contains nature orbitals, the latter contains density matrix, both of them corresponding to MP2 relaxed density.

Then rename .mp2nat as .gbw

mv h2o.mp2nat h2o.gbw

Use h2o.gbw as input file for Multiwfn to carry out ESP analysis as I described in 1#, then use below command to calculate ESP on surface vertices:

orca_vpot h2o.gbw h2o.pmp2re surfptpos.txt out.txt

The resulting out.txt records ESP corresponding to MP2 relaxed density.

Reduce cost of ESP analysis on molecular surface for ORCA users

dummy@example.com (sobereva) — Thu, 05 Mar 2020 21:20:09 +0000

As shown in Section 5.7 of Multiwfn manual, Gaussian user can use cubegen utility to significantly reduce cost of electrostatic potential (ESP) analysis in Multiwfn, however if you are unable to access Gaussian package and you are an ORCA user, fortunately, you can use orca_vpot utiliy in ORCA to save computational cost. Below an example is given.

Perform a regular single point calculation for water

! B3LYP def2-SVP keepdens
%maxcore 1000
%pal nprocs  4 end
* xyz   0   1
O     -0.00000000   -0.00000000    0.11930801
H      0.00000000    0.75895306   -0.47723204
H     -0.00000000   -0.75895306   -0.47723204
 *

After calculation, you can find h2o.gbw and h2o.scfp in current folder, the latter records density matrix.

Run below command to convert h2o.gbw file to h2o.molden.input

orca_2mkl h2o -molden

PS: This step can be skipped if orca_2mklpath in settings.ini file of Multiwfn has been set to actual path of orca_2mkl, because in this case Multiwfn can directly open .gbw file by automatically invoking orca_2mkl.

Boot up Multiwfn and input
h2o.molden.input
12 // Quantitative analysis of molecular surface
5 // Let Multiwfn load mapped function values from external file
1 // Load mapped function at all surface vertices from plain text file
0 // Start analysis

Now you can find surfptpos.txt in current folder, which contains position of all surface vertices. Put it to the folder containing h2o.gbw and h2o.scfp, then run below command in this folder

orca_vpot h2o.gbw h2o.scfp surfptpos.txt out.txt

The outputted out.txt contains ESP value of surface vertices.

Now, input the path of the out.txt file in Multiwfn window, Multiwfn will load ESP from this file and then analyze ESP on molecular surface.