Talk:Partial charge

List of charge schemes

I think that the list of atomic partial charge schemes should be a separate "List" page. It seems that more and more atomic partial charge schemes are being published, so listing them under a heading "The following is a detailed list of earlier methods, partly based on Meister and Schwarz (1994)." is no longer true (newer methods are being added under this list). It makes sense that from there, people may create separate pages that discuss how each method works. Sirjasonr (talk) 03:07, 12 June 2013 (UTC)
I removed the "earlier methods" text and stated that it is simply a list of methods. I removed the paragraph that began with "The closest equivalent quantum-mechanical (QM) methods to derive atomic charges for molecular simulations are computations of the electron density at a high level of theory in combination with Hirshfeld partitioning of the charge density into approximately spherical atomic basins." because many studies have shown the Hirshfeld method systematically underestimates the magnitudes of partial charges. I also removed the paragraph "Not surprisingly, approaches based on quantum mechanics have therefore questioned the concept of partial atomic charge as somewhat arbitrary. The results depend on the initial guess of the wave function and the method used to delimit between one atom and the next, related to the spatial continuity of the electron density. In spite of experimental data that have shown that boundaries between atoms and shifts in electron density are often well enough defined, many QM procedures have been developed for estimating the partial charges, yet are recommended with caution due to the wide range of assumptions and scatter." In place of these two paragraphs, I inserted a paragraph describing the current state of the art and explaining the deficiencies of some older methods. The removed paragraph contained "Besides, different partitioning schemes such as by Mulliken or by Bader can lead to additional overestimates in atomic charges by over 30% compared to Hirshfeld charges.". This statement was highly problematic, because it compared results of two charge methods to another rather than comparing all three to experimental results. In place of the problematic statement, I inserted sentences describing the main limitations of the Hirshfeld, Mulliken, and Bader charges. The removed paragraph also contained another problematic sentence: "Overall, ab-initio studies today suggest atomic charges with uncertainties up to multiples while available laboratory measurements since the 1950s quantify atomic charges consistent with known physical chemical properties within a range of ±5-10%. " This sentence was problematic, because the uncertainty in extracting partial charges from experimental data is usually more than 5-10%. The new paragraph focuses on the current state of the art and describes some key limitations of older methods.--Blue rover (talk) 22:24, 28 April 2017 (UTC)

Lead in need of improvement

This is an important if not fundamental concept in chemical bonding theory, so I changed the importance rating to mid. Please read the second paragraph of the lead. I'm not sure I understand what the point is, and usage of terms like "oscillates" and "zones" makes me think that the author had serious terminological if not conceptual misunderstandings. I feel that it needs to be deleted, but I'm not sure what should take its place. Alsosaid1987 (talk) 06:28, 19 June 2019 (UTC)