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La transformación estructural en el agua súper enfriada controla la tasa de cristalización del hielo
Emily B Moore1, Valeria Molinero
1Department of Chemistry, University of Utah, Salt Lake City, Utah 84112-0580, USA.
Nature
|November 25, 2011
Resumen
Los investigadores exploraron el agua súper enfriada.
Área de la Ciencia:
- Química Física es la química física.
- Ciencia de los materiales Ciencia de los materiales.
- La termodinámica es la termodinámica.
Sus antecedentes:
- La temperatura más baja para el agua súper enfriada antes de la cristalización del hielo sigue siendo un rompecabezas sin resolver.
- Los estudios experimentales están limitados por debajo de la temperatura de nucleación homogénea (T(H) ≈ 232 K) debido a la rápida cristalización.
- Las propiedades termodinámicas anómalas del agua líquida en la región superenfriada sugieren un vínculo con las tasas de cristalización del hielo.
Objetivo del estudio:
- Para investigar el mecanismo de cristalización del hielo en agua súper enfriada.
- Comprender la relación entre la termodinámica anómala del agua y su tasa de cristalización.
- Determinar los factores que controlan la velocidad y los mecanismos de formación de hielo en agua súper enfriada.
Principales métodos:
- Simulaciones moleculares de grano grueso utilizando el modelo de agua mW.
- Análisis de la fracción de moléculas de cuatro coordenadas en agua líquida súper enfriada.
- Integración con la teoría clásica de la nucleación y los datos experimentales.
Principales resultados:
- Un fuerte aumento de las moléculas de cuatro coordenadas en el agua súper enfriada explica su termodinámica anómala.
- Esta transformación estructural controla la velocidad y los mecanismos de formación de hielo.
- La tasa de cristalización del agua alcanza su punto máximo alrededor de 225 K, lo que indica una nucleación de hielo más rápida que el equilibrio líquido por debajo de esta temperatura.
Conclusiones:
- Un límite inferior de metastabilidad para el agua líquida existe justo por debajo de T(H).
- El estudio establece un vínculo mecánico entre los cambios estructurales del agua líquida, la termodinámica y la cristalización.
- Los hallazgos proporcionan información sobre las tasas de nucleación de hielo homogéneo y su dependencia de las propiedades termodinámicas del agua.
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