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Solidification Kinetics

  Atomic Smoothness of Interface (ii)     4 of 7

have a go!Move the mouse over different DSf / k ratios to see a schematic representation of this effect

The probability of an interfacial molecule being melted off, i.e. the fraction of this type of molecule which will be detached, is given by a Boltzmann expression  . Comparison of these probabilities gives a picture of the smoothness of the interface. For example, a smooth interface will be one for which there are few remaining molecules with n=1 and many with n=5, i.e. for which this ratio is large

Using the expression DSf = DHf / Tf, and assuming that the temperature is close to Tf, this ratio can be written as .  

A high value (10) for this ratio, obtained when DSf / k is greater than about 5-6, will give a smooth interface.



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