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Atom Positions in Highly Ordered Kaolinite

Published online by Cambridge University Press:  02 April 2024

P. R. Suitch  and
R. A. Young
P. R. Suitch
Affiliation:
School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332
R. A. Young
Affiliation:
School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332
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Abstract

The crystal structure of kaolinite(Pl, a = 5.153(1), b = 8.941 (1), c = 7.403 (1)Å, α = 91.692(3)°, β = 104.860(3)°, γ = 89.822(3)°, specimens from Keokuk geodes) has been refined in detail and that of dickite (Cc, a = 5.1460(3), b = 8.9376(5), c = 14.4244(6) Å, β = 96.761(5)°) has been re-refined, both from powder diffraction data with the Rietveld method. Except for the hydrogen atoms, the layer structures in both clays are very similar and are much as inferred or determined previously by others. The rotation in the tetrahedral sheet is 7(1)°. The two inner hydroxyl O-H bonds in kaolinite are differently oriented; one points into an octahedral vacancy and the other somewhat away from the octahedral sheet and toward the unoccupied center of an oxygen triangle formed by the two apical oxygens and shared basal oxygen of two adjacent SiO4 tetrahedra. All six of the inner surface hydrogen atoms appear to be nearly equally involved in the hydrogen bonding between kaolinite layers in kaolinite.

Резюме

Резюме

На основе данных рентгеновской порошковой дифракции, обработанных по методу Ретвельда, была подробно усовершенствована кристаллическая структура каолинита (Pl, a = 5,153(1), b = 8,941(1), с = 7,403(1) Å, α = 91,692(3)°, β = 104,860(3)°, γ = 89,822(3)°, образцы из кеокуовых жеод), а также более усовершенствована кристаллическая структура дикита (Сс, a = 5.1460(3), b = 8.9376(5), с = 14,4244(6) Å, β = 96.761(5)°). Эа исключением атомов водорода, слоистые структуры обоих глин являются подобными и находятся в соответствии со структурами, ранее определенными другими исследователями. Вращение в тетраэдрическом слое составляет 7(1)°. Две внутренние связи О-Н в каолините ориентированы по-разному; одна направлена в сторону октаэдрической пустоты, а другая направлена немного в сторону от октаэдрического слоя и по направлению к незанятому центру кислородного треугольника, образованного из двух апикальных атомов кислорода и одного основного атома кислорода, делииого между двумя прилегающими четырехгранниками SiO4. Все шесть атомы водорода внутренней поверхности, По-видимому, почти по-равному участвуют во водородных связях между каолинитовыми слоями в каолините. [E.G.]

Resümee

Resümee

Die Kristallstruktur von Kaolinit (Pl, a = 5,153(1), b = 8,941(1), c = 7,403(1) Å, α = 91,692(3)°, β = 104,860(3)°, γ = 89,822(3)°, Proben von Keokuk Geoden) wurden im Detail verfeinert und die von Dickit (Cc, a = 5,1460(3), b = 8,9376(5), c = 14,4244(6) Å, β = 96,761(5)° wurden noch einmal verfeinert. Bei beiden Mineralen wurde dies anhand der Röntgenpulverdaten nach der Rietveld-Methode durchgeführt. Mit Ausnahme der Wasserstoffatome sind die Lagenstrukturen in beiden Tonen sehr ähnlich und entsprechend weitgehend den Strukturen, die bereits von anderen Autoren vorgeschlagen oder bestimmt wurden. Die Rotation in den Tetraederschichten beträgt 7(1)°. Die beiden inneren Hydroxyl O-H Bindungen im Kaolinit sind unterschiedlich orientiert; die eine zeigt in eine oktaedrische Lücke und die andere etwas von der Oktaederschicht weg und in Richtung des unbesetzten Zentrums eines Sauerstoff-dreiecks, das durch zwei apicale Sauerstoffe und dem gemeinsamen Sauerstoff von zwei benachbarten SiO4-Tetraedern gebildet wird. Alle sechs inneren Oberflächen-Wasserstoffatome scheinen nahezu zu gleichen Teilen an der Wasserstoffbindung zwischen den Kaolinitlagen im Kaolinit beteiligt zu sein. [U. W.]

Résumé

Résumé

La structure cristalline de la kaolinite (Pl, a = 5,153(1), b = 8,941(1), c = 7,403(1) Å, α = 91,692(3)°, β = 104,860(3)°, γ = 89,822(3)°, spécimens de géodes de Keokuk) a été raffinée en détail, et celle de la dickite (Cc, a = 5,1460(3), b = 8,9376(5), c = 14,4244(6) Å, β = 96,761(5)°) a été re-raffmée, toutes deux à partir de données de diffraction avec la méthode de Rietveld. A part les atomes d'hydrogène, les structures de couches dans les deux argiles sont très semblables et sont proches de ce que d'autres avaient précedemment inféré ou déterminé. La rotation dans le feuillet tétraèdral est 7(1)°. Les deux liens intérieurs hydroxyls O-H dans la kaolinite sont orientés différemment; l'un se dirige vers un site octaèdral vacant, et l'autre quelque peu dans une direction opposée à la feuille octaèdrale et vers le centre inoccupé d'un triangle oxygène formé par les deux oxygènes apiquaux et l'oxygène basal partagé par deux tetràedres SiO4 adjacents. Les six atomes d'hydrogène de la surface intérieure semblent etre presque également impliqués dans les liens d'hydrogène entre les couches de kaolinite dans la kaolinite. [D.J.]

Keywords

Crystal structureDickiteHydrogen atomHydroxyl orientationKaoliniteRietveld method
Type
Research Article
Information
Clays and Clay Minerals , Volume 31 , Issue 5 , October 1983 , pp. 357 - 366
Copyright
Copyright © 1983, The Clay Minerals Society

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