[Cod-bugs] meaning of 'At' and 'Ow" in zeolite structure

Saulius Gražulis grazulis at ibt.lt
Tue Aug 10 10:13:56 EEST 2021

Dear Fabio!

On 2021-08-10 01:17, Fabio Ramos Dias de Andrade wrote:
> what is the meaning of 'At', in a formula such as 
> Reference code: 96-900-6365

The reference code (aka database ID) does not seem to belong to any of
our curated or related databases (COD, PCOD, TCOD, AMCSD).

For the experimental databases (COD, AMCSD), the IDs are 7-digit
numbers, but you quote nine digits. We can not trace back that data.
Please either provide the COD ID for the data you are working with, or
the database designator from which you reference code was taken; only
then the data provenance can be established.

> Mineral name: Laumontite
> Compound name: Laumontite
> Common name: Laumontite
> Chemical formula: Si16.00Al8.00O48.00Ca4.00*At23.08*H37.60
Usually, "At" in CIFs means Astatine, or Astatium [1]. It is strange
however to see this element in such abundances in an X-ray experimental
structure, since all isotopes of AT are unstable, and the most stable
has half-life of just 8.3 hours [1]. It would be difficult (although not
impossible) to obtain crystals containing At for long enough to measure
their structure. For zeolites, of course, At could be a "guest"
component that was diffused rapidly (as a solute or in gaseous form)
into the structure and the measured on a synchrotron or on a neutron source.

Another possibility could be that "At" is mistyped "Al", although this
is unlikely since Al is already present in the formula.

In any case you should refer to the original publication that reported
the structure – you should find there exact description of the sample
and its preparation.

Hope this helps!


[1] https://www.webelements.com/astatine/ [2021-08-10 10:07:00+03:00]

Dr. Saulius Gražulis
Vilnius University, Life Science Center, Institute of Biotechnology
Saulėtekio al. 7, LT-10257 Vilnius, Lietuva (Lithuania)
phone (office): (+370-5)-2234353, mobile: (+370-684)-49802, (+370-614)-36366

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