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Orientational Transition in a Liquid Crystal Triggered by the Thermodynamic Growth of Interfacial Wetting Sheets
Published on: May 15, 2017
Dinámica de una transición de fase de segundo orden: P macr; a la transición de fase I1 en anortita, CaAl2Si2O8
Science (New York, N.Y.)
|December 23, 1988
Resumen
Un estudio con microscopio electrónico revela que los límites antifásicos de la anortita se vuelven inestables a su temperatura de transición, formando bucles móviles. Este comportamiento dinámico sugiere que las vibraciones de la red impulsan la transición de fase reversible de P1 a I1.
Área de la Ciencia:
- Física mineral Física de los minerales
- La cristalografía es una técnica de cristalografía.
- Ciencia de los materiales Ciencia de los materiales.
Sus antecedentes:
- La anortita exhibe una transición de fase reversible entre las estructuras P1 e I1 a 516 Kelvin.
- Los límites antifásicos (APB) son características microstruturales críticas que influyen en las transiciones de fase.
Objetivo del estudio:
- Para investigar el comportamiento de los límites antifásicos durante la transición de fase P1 a I1 en anortita utilizando microscopía electrónica.
- Para dilucidar el mecanismo que impulsa la transición de fase reversible a nivel atómico.
Principales métodos:
- Se empleó microscopía electrónica de alta resolución para observar la estructura de la anortita.
- El control de la temperatura in situ permitió el estudio de la dinámica de la transición de fase.
Principales resultados:
- Los límites antifásicos con un vector de desplazamiento de R = 1/2[111] se vuelven inestables cerca de la temperatura de transición (T(c)).
- Numerosos bucles de frontera antifase pequeños y altamente móviles se forman y aumentan la frecuencia de vibración con la temperatura.
- Se propone que las vibraciones del enrejado, específicamente los tipos de movimiento de respiración, faciliten el intercambio dinámico de configuraciones alrededor de los átomos de calcio.
Conclusiones:
- La estructura I1 de alta temperatura de la anortita representa un promedio estadístico-dinámico de los dominios móviles antifase.
- La dinámica del enrejado juega un papel crucial en el mecanismo de transición de fase reversible de P1 a I1 en la anortita.
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