Farhan Khan

Assalam o alaikum wa rahmatullahi wa barkatahu

Hope you doing well

Open the .chk file in gaussian then go to result and click on surface and contour-> cube action-> option and select of new cube->generate cubes-> type-> select total density click on ok and after loading electron density go below on surface actions-> select new mapped surface-> surface mapping open-> click on type-> select ESP then ok after few minutes generate the nucleophile and electrophile region which shows red and blue color and see below the title bar shows a color strip which denoted in negative and positive value and see attach file.

If I got It correctly, you mean the electronic density itself? You can extract tons of interesting and very useful information from it (as long as printed in a wfn/wfx/FChk file) using programs like AIMAll or Multiwfn. They handle various topological analysis (including, but not limited to, QTAIM). These topological properties até related to energy, geometries, reactivity, conformation, etc.

First note that Gaussian is able to generate wavefunction, which can then be converted to electron density and then plotted by for example Multiwfn (as curve map, plane map, isosurface map, etc.), while Gaussian itself doesn't have any function for graphically plotting density.

Usually plotting total electron density is not useful, but plotting valence electron density is often able to provide chemically useful information, this point has been illustrated in my paper "Revealing Molecular Electronic Structure via Analysis of Valence Electron Density" (http://www.whxb.pku.edu.cn/EN/10.3866/PKU.WHXB201709252).