[Cod-bugs] Incorrect structure + spelling mistake - COD ID 1526591

David Palmer david at crystalmaker.com
Fri Mar 9 16:05:59 EET 2018

Dear Sir/Madam,

I recently came across a question about the crystal structure of the element gadolinium. One of our users had shown me a double-hexagonal-close-packed (“dhcp") structure, but Wyckoff claimed the element had a simple hcp structure. We took a look at your database and found that one of your structures appears to be incorrect. Here are the details:-

COD ID: 1526591

There are two issues here:-

1. Spelling mistake in the journal title “Supercondunctivity” (remove the second ’n’).

2. The structure makes no sense.

- I don’t know whether some information has been lost here, but your CIF file lists only a single site, at {1/2, 1/2, 1/2} - which is a (very) special position. When plotted, this quite large unit cell only has this single atom - which is clearly incorrect.

- If one is using an orthorhombic unit cell (for what is effectively an hexagonal lattice), then I would expect the ‘a’ or ‘b’ parameter to be much larger, something on the order of 6.3 Å (=2 . aH . cos(30), where ‘aH’ is the hexagonal parameter) - unless this is supposed to be some kind of derivative of the higher-temperature (“beta”) bcc lattice.

I hope this information helps!

With best wishes,

David Palmer
Managing Director,
CrystalMaker Software Ltd

CrystalMaker is a user-funded project to provide the very-best software for crystal and molecular structures modelling.

We receive no EU subsidies, government bailouts, university salaries, pensions or student fee income. Everything we do is funded by our users - not the general taxpayer. It’s the only honest and sustainable way of providing quality software for the long term.
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