Multiwfn forum

ffuser

Member

Registered: 2020-10-20

Posts: 9

Molecular surface analysis of density difference

Hi,

I’d like to ask how to make a histogram using density difference on a molecular surface.
(Density difference between ground and excited states)

What I want to do is similar to the description in “quantitative analysis of molecular surface” in the manual.
There, I found a histogram with horizontal axis representing ESP and vertical axis representing surface area.
I’m trying to make a histogram with horizontal axis representing density difference and vertical axis representing surface area, instead.

My current situation is that I successfully made density difference cube file by cubman, “su” operation.
(I visualized this cube file on gaussview and confirmed the file was properly created)
So far, I obtained ground state density cube, excited state density cube, and density difference between them.
However, I don’t know how to proceed further.

Could anyone help? Thanks in advance.

Last edited by ffuser (2020-10-21 02:53:14)

sobereva

Tian Lu (Multiwfn developer)

From: Beijing

Registered: 2017-09-11

Posts: 1,830

Website

Re: Molecular surface analysis of density difference

Hello,

There are two ways:

(1) If you already have wavefunction file of ground state and excited state, you can simply follow the example in Section 4.12.4 of Multiwfn manual. This section illustrated how to quantitatively analyze Fukui function f- on vdW surface, the f- function is essentially the density difference between N and N-1 states, where N is the number of electrons in original state.

If you have reproduced this example, you must naturally know how to quantitative analyze the distribution of the density difference between ground state and excited state.

(2) If you only have cube file of electron density, in the main function 12, you can choose "5 Loading mapped function values from external file", then choose "3 Mapped function will be interpolated from an external cube file". In this case, after starting the analysis by option 0, Multiwfn will ask you to input a cube file, the mapped function on molecular surface will be evaluated by interpolation based on the data of this cube file. (However, note that, the grid setting in this inputted cube file must be exactly identical to the template cube file, which is automatically exported by Multiwfn after choosing "0 Start analysis now!", see prompts on screen)

Note that Multiwfn is able to easily calculate grid data and export cube file for electron density difference, see e.g. Section 4.18.3 of manual.

ffuser

Member

Registered: 2020-10-20

Posts: 9

Re: Molecular surface analysis of density difference

Thank you so much.
Following 4.18.3, 4.12.4 and 4.12.1, I successfully made histogram of density difference on a molecular surface.
I’m so grateful to your help.