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La nucleación de hielo homogéneo en superenfriamiento moderado de simulación molecular
1Departamento de Química Física, Facultad de Ciencias Químicas, Universidad Complutense de Madrid , 28040 Madrid, Spain.
Journal of the American Chemical Society
|September 10, 2013
Resumen
Este estudio explora la nucleación homogénea de hielo en el agua utilizando simulaciones por computadora. Los resultados indican que por encima de 20 K por debajo del punto de fusión, la congelación del agua debe ser heterogénea, no homogénea.
Área de la Ciencia:
- Física Física es la física de las cosas.
- Química Química es la química.
- Geología Geología Geología.
Sus antecedentes:
- La congelación del agua en hielo es una transición crítica en múltiples disciplinas científicas.
- Comprender la nucleación homogénea del hielo es clave para explicar los fenómenos naturales de congelación.
Objetivo del estudio:
- Para investigar la nucleación de hielo homogéneo en el agua a través de simulaciones por computadora.
- Para determinar el tamaño crítico del cúmulo y la tasa de nucleación a varias temperaturas bajo cero.
Principales métodos:
- Utilizó los modelos TIP4P/2005 y TIP4P/agua de hielo para las simulaciones.
- Empleó la Teoría de la Nucleación Clásica (CNT) para analizar las barreras de la energía libre.
- Agrupaciones críticas simuladas en el ápice de la barrera de nucleación.
Principales resultados:
- El tamaño crítico del racimo disminuye de ~8000 moléculas (4 nm) a ~600 moléculas (1.7 nm) a medida que la temperatura cae de 15 K a 35 K por debajo del punto de fusión.
- La energía libre calculada de la interfaz hielo-agua es de 293 mN/m, consistente con los datos experimentales.
- Las tasas de nucleación simuladas se alinean con las mediciones experimentales, particularmente a temperaturas más bajas.
Conclusiones:
- Las tasas de nucleación de hielo homogéneo se vuelven extremadamente lentas a temperaturas superiores a 20 K por debajo del punto de fusión.
- Predice que toda la congelación del agua por encima de este umbral de temperatura debe ocurrir a través de la nucleación heterogénea.
- Los hallazgos concilian los resultados de la simulación con las observaciones experimentales del comportamiento de congelación del agua.
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