Talk:X-ray crystallography

GA Reassessment

X-ray crystallography

The following discussion is closed. Please do not modify it. Subsequent comments should be made on the appropriate discussion page. No further edits should be made to this discussion.

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Article (edit | visual edit | history) · Article talk (edit | history) · Watch • Watch article reassessment page • Most recent review

Result: Per the discussion at WT:GAR#Please keep topical limits in mind and below, this chemistry article is far below the GA criteria. ~~ AirshipJungleman29 (talk) 18:24, 15 February 2023 (UTC)

GA from 2008. There's some uncited information including

• Finally, X-ray crystallography had a pioneering role in the development of supramolecular chemistry, particularly in clarifying the structures of the crown ethers and the principles of host–guest chemistry. X-ray diffraction is a very powerful tool in catalyst development. Ex-situ measurements are carried out routinely for checking the crystal structure of materials or to unravel new structures. In-situ experiments give comprehensive understanding about the structural stability of catalysts under reaction conditions. In material sciences, many complicated inorganic and organometallic systems have been analyzed using single-crystal methods, such as fullerenes, metalloporphyrins, and other complicated compounds. Single-crystal diffraction is also used in the pharmaceutical industry, due to recent problems with polymorphs. The major factors affecting the quality of single-crystal structures are the crystal's size and regularity; recrystallization is a commonly used technique to improve these factors in small-molecule crystals. The Cambridge Structural Database contains over 1,000,000 structures as of June 2019; over 99% of these structures were determined by X-ray diffraction.
• which is on the scale of covalent chemical bonds and the radius of a single atom. Longer-wavelength photons (such as ultraviolet radiation) would not have sufficient resolution to determine the atomic positions. At the other extreme, shorter-wavelength photons such as gamma rays are difficult to produce in large numbers, difficult to focus, and interact too strongly with matter, producing particle-antiparticle pairs. Therefore, X-rays are the "sweetspot" for wavelength when determining atomic-resolution structures from the scattering of electromagnetic radiation.
• The Electron and Neutron diffraction section.
• Each spot is called a reflection, since it corresponds to the reflection of the X-rays from one set of evenly spaced planes within the crystal. For single crystals of sufficient purity and regularity, X-ray diffraction data can determine the mean chemical bond lengths and angles to within a few thousandths of an angstrom and to within a few tenths of a degree, respectively. The atoms in a crystal are not static, but oscillate about their mean positions, usually by less than a few tenths of an angstrom. X-ray crystallography allows measuring the size of these oscillations.

And many more. Onegreatjoke (talk) 21:30, 7 February 2023 (UTC)

Saw the post at WT:MOLBIO. Woof, this article is a beast. Just in the History section this article needs some heavy lifting:

1. Too much detail/Not enough detail - some of this is undue and should be merged into the History section of X-ray or trimmed. Some is not about History and should be moved to the Theory section (e.g. the top of the "X-ray diffraction" subsection). Partly it's to make the section more readable, but also we need to make space to discuss the post-1920 history of crystallography in greater detail. This history section would make you think we stopped using X-ray crystallography 100 years ago. See this (very long) review to fill in some of the gaps.
2. Wrong citations - The History section is written like a scientific review article. The references are links to scientific works of the distant past, rather than actually supporting the claim that so-and-such discovered this-and-that.

I haven't made it further yet. But unless someone else is interested in working on this, I'm afraid it'll be a task beyond the time I have available. Ajpolino (talk) 23:11, 7 February 2023 (UTC)

The discussion above is closed. Please do not modify it. Subsequent comments should be made on the appropriate discussion page. No further edits should be made to this discussion.

Technical Limit

I removed a paragraph that cited an error made 32 years ago, due to technical limits in the software and hardware, which no longer exist. These limits were overcome before Wikipedia was initiated. No where else does this article cite papers that were wrong due to limits in the technology at the time the work was done. Nick Beeson (talk) 20:07, 25 October 2023 (UTC)

While obviously science is self-correcting (we hope) and we don't use our own editorial interest to highlight old mistakes, this specific mistake has itself been covered as a highlight of what happened and why. Therefore I think it is quite WP:DUE to mention it. See for example doi:10.1002/anie.200460864. DMacks (talk) 03:17, 26 October 2023 (UTC)

For clarity, we're talking about Special:Diff/1181882695 (and the later Special:Diff/1188605822) here. I am not quite able do anything useful right now, but I do feel like talking about some problems is useful. I don't immediately recall anything recent about small-ish molecules like in the 32-year-old case, but it does remind me of a previously-unknown post-translation modification being missed despite visible density (doi:10.1038/s41589-021-00966-5).

...whether a mention like this is good for GA assessment purposes (length) is beyond the current capabilities of my head. Artoria2e5 🌉 11:22, 15 December 2023 (UTC)

For a GA reassment what is needed first is references (sources), as way too much has none. Can you help? Ldm1954 (talk) 17:16, 15 December 2023 (UTC)

X-ray crystallography is based on Thomson scattering.

The last sentence of Thomson scattering links this page with an unreferenced claim: "X-ray crystallography is based on Thomson scattering.". Maybe someone here has a reference handy that could be added? Even better would be another sentence explaining why. Johnjbarton (talk) 18:06, 30 November 2023 (UTC)

Section on Women in x-ray crystallography moved from Crystallography

The section on #Contributions of women to x-ray crystallography came originally from Crystallography. It seems more appropriate here, although parts (e.g. international tables) could be in both. Ldm1954 (talk) 19:27, 6 December 2023 (UTC)

Split x-ray diffraction and crystallography

The two are not the same, and there are many areas of XRD where the focus is not on detailed determination of atomic positions. Examples are powder diffraction where comparison is made to known samples, SAXS and many more. There are many areas/pages where it is relevant to say "use XRD" but wrong to say use "X-ray crystallography". I am posting here for comment before doing it. Ldm1954 (talk) 07:35, 14 April 2024 (UTC)

Thanks for posting the question. It might be better then to change the name of the article to X-Ray Diffraction, and then X-ray crystallography becomes a major heading within it. It's just misnamed. Martino3 (talk) 04:24, 18 April 2024 (UTC)

The current article has stacks on structure determination, which is I argue is "X-ray crystallography" so should stay there. Then XRD can be cleaner Bragg/Kinematical with a bit on dynamical, SXRD and perhaps small angle and soft/white diffraction etc. Plenty there that is not crystallography. Yes? Ldm1954 (talk) 04:30, 18 April 2024 (UTC)

Perhaps approaching this from the reverse direction would help clarify the possibilities: reorg this article to more clearly identify the XRD content. In other words, the current article looks like x-ray crystallography with some muddiness from XRD, but if the XRD part were clearer then it would look like two articles that should be split. Johnjbarton (talk) 15:03, 18 April 2024 (UTC)

We have an existing powder diffraction article that seems quite detailed and includes X-ray as well as other types of radiation, and a few other diffraction-related articles. I like Johnjbarton's idea of keeping this X-ray crystallography article on its named topic and working on moving content not strictly on that topic to other articles (maybe even new ones). Maybe a start would be X-ray diffraction as a WP:SUMMARYSTYLE parent of powder diffraction, X-ray crystallography, X-ray scattering techniques (which itself is a parent of SAXS, WAXS, etc.), etc. That could help us find better homes for content here that is not on this article's narrowed topic. DMacks (talk) 15:42, 18 April 2024 (UTC)

For DMacks mainly, X-ray scattering is (and should remain) the overall summary as it includes both elastic and inelastic. X-ray crystallography is all about solving, PXRD is different (and I know ICDD want to rewrite that page). Small steps to clean a massive area.

As a very rough guide, see User:Ldm1954/Sandbox/XRD for what would be removed from this article and form the core of an XRD page. Very rough Ldm1954 (talk) 03:35, 19 April 2024 (UTC)

I am reviving X-ray diffraction (as stated on the crystallography page as well as here and a couple of other places for discussion some time ago), moving selected material from X-ray crystallography, where contributors can be found. More work is needed, this is just the first pass. Ldm1954 (talk) 07:59, 1 May 2024 (UTC)

I suspect that they are used, often enough, synonymously, even if technically they should not be. For one, it is still crystallography on amorphous, or non-crystalline solids. Someone once claimed that crystallography is the best path to a Nobel prize, based on statistics of prize winners. On the other hand, it might be that this one is long enough for two articles. It is crystallography if done by a crystallographer, even if not done on crystals. Gah4 (talk) 11:42, 1 May 2024 (UTC)

Sorry, as a professional crystallography I need to point out that this is not right. X-ray diffraction is diffraction using X-rays, similar to electron diffraction. X-ray crystallography is crystallography using X-rays, comparable to electron crystallography. Diffraction is an elastic process with photons, matter waves etc. Crystallography is about determining atomic positions, it is not about mineral crystals despite the name.

N.B., yes, there have been many nobels in X-ray crystallography, and relatively few (von Laue, the Braggs) for X-ray diffraction,see the list in the article. Ldm1954 (talk) 12:02, 1 May 2024 (UTC)

OK, but what do you do with X-ray diffraction other than X-ray crystallography? One of the more amazing things to me, is that the lattice constant of silicon is known to 10 significant digits. Maybe you don't count measuring that as crystallography, though. Gah4 (talk) 19:58, 2 May 2024 (UTC)

Many other uses beyond crystallography, for instance phase identification by comparison, determination of the composition of mixtures, thermal expansion, disorder, phase transitions, texture, orientation, epitaxy..the list is long and there is much more than I have listed. Ldm1954 (talk) 05:48, 3 May 2024 (UTC)