I am a beginner to this particular side of the theoretical analysis of a molecule using Gaussian and GaussView. What do the isovalues mean? What physical significance do they hold? How does one choose an appropriate value for an isovalue? Is it based on trial and error, by looking at the plot of the ESP?
Also, along the same lines, what useful information can we gather from the ESP after having chosen an appropriate isovalue?
I have come across this analysis in a recent online conference and am trying to apply it to my molecule of interest. Though I was able to read up on how to perform such an analysis using GaussView, there are these basic questions lingering in my mind. I also came across the concept of a critical point in this analysis. Though I have no idea what that means or how to obtain it, if someone could throw light on this, I would consider it as a bonus :)
https://www.researchgate.net/post/How-to-interpret-a-map-of-electrostatic-potential-MEP
An isosurface consists of numerous surface vertices, function value at these points exactly equals to the given isovalue. Therefore, different choices of isovalue result in different isosurface.
A popular way of studying distribution of ESP is mapping it on vdW surface, which is usually defined as isosurface of rho=0.001 a.u. (Bader's vdW surface definition for gas phase). See some of my works for discussion examples: Carbon, 171, 514 (2021) DOI: 10.1016/j.carbon.2020.09.048, RSC Adv., 5, 78192 (2015) DOI: 10.1039/c5ra17148b, Struct. Chem., 25, 1521 (2014) DOI: 10.1007/s11224-014-0430-6. I prefer to plot this kind of map via Multiwfn and VMD, both of them are freely available, and and there is a video illustration: https://youtu.be/QFpDf_GimA0. This video also exhibited how to show ESP extrema on molecular vdW surface (probably they are the "critical point" you mentioned in the current context).
- Badges
- Science topic