http://www.cnr.it/ontology/cnr/individuo/prodotto/ID255816

Neutron diffraction in gemology: Single-crystal diffraction study of brazilianite, NaAl3(PO4)2(OH)4 (Articolo in rivista)

Type

Articolo in rivista (Classe)
Prodotto della ricerca (Classe)

Label

Neutron diffraction in gemology: Single-crystal diffraction study of brazilianite, NaAl3(PO4)2(OH)4 (Articolo in rivista) (literal)

Anno

2013-01-01T00:00:00+01:00 (literal)

Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#doi

10.2138/am.2013.4476 (literal)

Alternative label

G. Diego Gatta1, Pietro Vignola1, Martin Meven2,3, Romano Rinaldi4 (2013)
Neutron diffraction in gemology: Single-crystal diffraction study of brazilianite, NaAl3(PO4)2(OH)4
in The American mineralogist; Mineralogical Society of America, Washington (Italia)
(literal)

Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori

G. Diego Gatta1, Pietro Vignola1, Martin Meven2,3, Romano Rinaldi4 (literal)

Pagina inizio

1624 (literal)

Pagina fine

1630 (literal)

Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#url

http://dx.doi.org/10.2138/am.2013.4476 (literal)

Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#numeroVolume

98 (literal)

Rivista

?The ?American mineralogist (Rivista)

Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#pagineTotali

7 (literal)

Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#affiliazioni

1Dipartimento di Scienze della Terra, Università degli Studi di Milano, Via Botticelli 23, I-20133 Milano, Italy 2Institut für Kristallographie, RWTH Aachen, Jägerstrasse 17-19, D-52056 Aachen, Germany 3Jülich Centre for Neutron Science, Forschungszentrum Jülich GmbH, Outstation at FRM II, Lichtenbergstrasse 1, D-85747 Garchin 4Dipartimento di Scienze della Terra, Università degli Studi di Perugia, Piazza Università 1, I-06123 Perugia, Italy (literal)

Titolo

Neutron diffraction in gemology: Single-crystal diffraction study of brazilianite, NaAl3(PO4)2(OH)4 (literal)

Abstract

The chemical composition and the crystal structure of a gem-quality brazilianite from the Telírio pegmatite, near Linópolis, Minas Gerais, Brazil, [NaAl3(PO4)2(OH)4, a = 11.2448(5) Å, b = 10.1539(6) Å, c = 7.1031(3) Å, b = 97.351(4)°, V = 804.36(7) Å3, space group P21/n, Z = 4], have been reinvestigated by means of electron microprobe analysis in wavelength-dispersive mode, single-crystal X-ray and neutron diffraction. The chemical analysis shows that brazilianite from Telírio Claim approaches almost ideal composition. The neutron anisotropic structural refinement was performed with final agreement index R1 = 0.0290 for 211 refined parameters and 2844 unique reflections with Fo > 4s(Fo), the X-ray refinement led to R1 = 0.0325 for 169 refined parameters and 2430 unique reflections with Fo > 4s(Fo). The building-block units of the brazilianite structure consist of chains of edge-sharing AlO4(OH)2 and AlO3(OH)3 octahedra. Chains are connected, via corner-sharing, by P-tetrahedra to form a three-dimensional framework, with Na atoms located in distorted cavities running along [100]. Five independent H sites were located, here labeled as H(1), H(2a), H(2b), H(3), and H(4). The configuration of the OH groups, along with the complex hydrogen-bonding scheme, are now well defined. The O-H distances corrected for \"riding motion\" range between ~0.992 and ~1.010 Å, the O···O distances between ~2.67 and ~2.93 Å, and the O-H···O angles between ~151° and ~174°. The H(2a) and H(2b) are only ~1.37 Å apart and mutually exclusive (both with site occupancy factor of 50%). The differences between the crystal structure of brazilianite and wardite [ideally NaAl3(PO4)2(OH)4·2H2O] are discussed. This work fulfills the need for accurate crystal-chemical data for this gem mineral (literal)

Editore