Hidden and apparent twins in uranyl-oxide minerals agrinierite and rameauite: a demonstration of metric and reticular merohedry

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00216224%3A14310%2F21%3A00123492" target="_blank" >RIV/00216224:14310/21:00123492 - isvavai.cz</a>

Result on the web

<a href="https://journals.iucr.org/j/issues/2021/06/00/vb5019/" target="_blank" >https://journals.iucr.org/j/issues/2021/06/00/vb5019/</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1107/S1600576721009663" target="_blank" >10.1107/S1600576721009663</a>

Result language

angličtina

Original language name

Hidden and apparent twins in uranyl-oxide minerals agrinierite and rameauite: a demonstration of metric and reticular merohedry

Original language description

In this work, the structures of chemically related uranyl-oxide minerals agrinierite and rameauite have been revisited and some corrections to the available structure data are provided. Both structures were found to be twinned. The two minerals are chemically similar, and though their structures differ considerably, their unit-cell metrics are similar. Agrinierite was found to be twinned by metric merohedry (diffraction type I), whereas the structure of rameauite is twinned by reticular merohedry (diffraction type II). The twinning of the monoclinic unit cells (true cells) leads to pseudo-orthorhombic or pseudo-tetragonal supercells in the single-crystal diffraction patterns of both minerals. According to the new data and refinement, agrinierite is monoclinic (space group Cm), with a = 14.069 (3), b = 14.220 (3), c = 13.967 (3) Å, β = 120.24 (12)° and V = 2414.2 (12) Å3 (Z = 2). The twinning can be expressed as a mirror in (101) (apart from the inversion twin), which leads to a supercell with a = 14.121, b = 14.276, c = 24.221 Å and V = 2 × 2441 Å3, which is F centered. The new structure refinement converged to R = 3.54% for 6545 unique observed reflections with I &gt; 3σ(I) and GOF = 1.07. Rameauite is also monoclinic (space group Cc), with a = 13.947 (3), b = 14.300 (3), c = 13.888 (3) Å, β = 118.50 (3)° and V = 2434.3 (11) Å3 (Z = 2). The twinning can be expressed as a mirror in (101) (apart from the inversion twin), which leads to a supercell with a = 14.223, b = 14.300, c = 23.921 Å and V = 2 × 2434 Å3, which is C centered. The new structure refinement of rameauite converged to R = 4.23% for 2344 unique observed reflections with I &gt; 3σ(I) and GOF = 1.48. The current investigation documented how peculiar twinning can be, not only for this group of minerals, and how care must be taken in handling the data biased by twinning.

Czech name

—

Czech description

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Type

J_imp - Article in a specialist periodical, which is included in the Web of Science database

CEP classification

—

OECD FORD branch

10504 - Mineralogy

Project

<a href="/en/project/EF16_026%2F0008459" target="_blank" >EF16_026/0008459: Long-term research of geochemical barriers for nuclear waste disposal</a><br>

Continuities

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)<br>I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Publication year

2021

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Name of the periodical

Journal of Applied Crystallography

ISSN

1600-5767

e-ISSN

1600-5767

Volume of the periodical

54

Issue of the periodical within the volume

6

Country of publishing house

GB - UNITED KINGDOM

Number of pages

8

Pages from-to

1656-1663

UT code for WoS article

000727770700013

EID of the result in the Scopus database

2-s2.0-85131185687