Identificación de patrones de difracción de micas
La practica usual de identificar micas mediante el valor de la difracción d060 del patrón de difracción, tiene ciertos inconvenientes y puede llevar a una identificación errónea. Pueden sacarse mejores conclusiones determinando los índices del patrón de difracción completo, especialmente si solo cansideramos al refinar los cálculos, aquellos planos en la estructura de la mica con alta densidad electrónica. Una solución intermedia es determinar la rnagnitud de d001 a partir de los planos 001 de alta densidad, la de d010 a partir de los Ok0 y Ok1, la de d100 a partir de los hOO y hkO, y el ángulo de las difracciones hO1 y hOl. los valores asi obtenidos pueden refinarse parcialmente usando el método de extrapolación de Taylor -Sinclair - Nelson - Riley. A B S T R A C T The comon practice of identifying micas by the value of the d060 difraction can lead to erroneous conclusions. There are usually several difractions around 0,15 n (1.5 A) and d060 is not necessarely the strong gest. The indexing of all diffractions and the least squares refinement of the lattice constants can yield more reliable results. However, when all geometrically possible hk1 planes are considered equally plausible, significant problems my be encountered because of the distinct geometric relationship between the magnitudes of the mica unit translations. That can be avoided by using only those dhk1´s in the initial refinement cycles, which are known to have electron density in practically all mica estructures. A simple method is offered for the determination of the values of d001 d100 and cos S fom high-intensity 001, OkO and Ok1, h00) and hkO and from hO1 and hOl diffractions, respectively, and from their linear refinement by the Taylor - Sinclair - Nelson - Riley extrapolation method. This method can executed both graphically and analytically. (A program designed for the II 59 calculator can be obtained from the authors).
| Main Authors: | , |
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| Format: | Digital revista |
| Language: | spa |
| Published: |
GEOS Revista Venezolana de Ciencias de la Tierra
2014
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| Online Access: | http://saber.ucv.ve/ojs/index.php/rev_geos/article/view/6849 |
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