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I have a rather general question of what software packages exist to do Quantum Theory Atom in Molecule (QTAIM) analysis of periodic and non-periodic systems. Working with Gaussian I have previously used Multiwfn. What other codes exist and what advantages/disadvantages do they have?

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    $\begingroup$ +1. So your answer would be about Multiwfn if no one else writes about it? Or were you thinking of answering with a different software? Does ChemTools or HORTON fit the bill? $\endgroup$ Sep 11 '20 at 19:19
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    $\begingroup$ Both of those tools look like they could work. I prefer not to self answer so I was only going to write about Multiwfn if nobody else does (I am by far not an expert in it). $\endgroup$ Sep 11 '20 at 19:21
  • $\begingroup$ Is this for your own calculations? $\endgroup$ Sep 16 '20 at 2:25
  • $\begingroup$ I don't have any immediate use for it, but my previous experience has me interested now. I no longer work on the types of systems which got me interested. $\endgroup$ Sep 16 '20 at 2:27
  • $\begingroup$ That's why I decided to start a bounty as well, it seems like most of these codes are for non-periodic calculations. I could not find a good resource comparing these codes. $\endgroup$ Sep 16 '20 at 2:29
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Critic2

critic2 is a very nice QTAIM code that supports interfaces to many codes, including also periodic systems: "WIEN2k, elk, PI, Quantum ESPRESSO, abinit, VASP, DFTB+, Gaussian, psi4, siesta, and to any other program capable of writing the scalar field of interest to a grid"

From personal experience, critic2 is very straight forward to compile and the developer is responsive to any issues, so definitely recommended!

Purely to calculate Bader charge basins, the Henkelman Bader tool is also very fast and reliable for specifically gridded data (VASP CHGCAR or Gaussian CUBE).

There is also a newer tool called TopoMS that promises improved robustness and has some compelling case-studies in its paper.

"QTAIM" itself is a broad topic, for example I'm not aware which tools currently available might be able to access information about, for example, bond bundles or other features.

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    $\begingroup$ This code supports libxc which is an interesting addition. $\endgroup$ Sep 17 '20 at 19:04
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Multiwfn

Multiwfn is a QTAIM package which supports most quantum chemistry codes, seemingly focusing on non-periodic systems. For example, from a formatted Gaussian checkpoint file it is capable of calculating cube files of properties such as the electrostatic potential or electron localization function. These properties can then be used for many advanced uses of which I have only personally explored a few in a recent article I worked on.

  • Critical point analysis of electron density: Identify bonds and lone pairs which exist in a molecule
  • Charge analysis of electron density: Identify partial oxidation states arising from polarized bonds or from charge transfer in complexes
  • Noncovalent interaction analysis (NCI): Identify where weak interaction/bonding is occurring as well as where steric effects are taking place within the molecule
  • Interaction Region Indicator (IRI) / Density Overlap Regions Indicator (DORI) analysis: Similar to NCI analysis but strong chemical bonding can also be visually seen.
  • Electrostatic potential analysis: Identify local maxima and minima on an isosurface of electrostatic potential. This allows for accurate quantification of the isosurface, compared to just visual identification.

Multiwfn was used to produce the following figure in this article showing an anion-anion bond. VMD was used to visualize the calculated NCI analysis from Multiwfn.

Interaction of I- interaction with I4Q-

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