Soft Matter and Complex Systems Seminar
sala 1.40, ul. Pasteura 5
2016-11-25 (09:30) 
Maciej Jasiński (CeNT UW)
The Mpemba Effect, do we really need an explanation?
We have used Molecular Dynamics simulations, to study process of water freezing with three different water models: TIP4P, OPC and TIP5P. In our simulations, systems containing water – air interface, were quenched from a range of temperatures to study effect of an initial conformation of water molecules onto an ice nucleation time and structure of formed ice.
We have observed ice nucleation in all investigated water models; interestingly that effect wasn’t reported previously for the TIP5P and OPC models. While it was suggested previously, that homogenous freezing of water starts in the subsurface, in our simulations the nucleation was observed both in the subsurface and the bulk water.
In agreement with the previous experiments, we observed in our simulations that initially warmer water sometimes freezes faster than the cold one. Interestingly, in our studies, similarly as in the available experimental works, we couldn't define a set of parameters that will ensure occurrence of that phenomenon. This may suggest that, observations of the Mpemba Effect are results of the stochastic nature of ice nucleation process, rather than manifestation of unknown water property.
We have observed ice nucleation in all investigated water models; interestingly that effect wasn’t reported previously for the TIP5P and OPC models. While it was suggested previously, that homogenous freezing of water starts in the subsurface, in our simulations the nucleation was observed both in the subsurface and the bulk water.
In agreement with the previous experiments, we observed in our simulations that initially warmer water sometimes freezes faster than the cold one. Interestingly, in our studies, similarly as in the available experimental works, we couldn't define a set of parameters that will ensure occurrence of that phenomenon. This may suggest that, observations of the Mpemba Effect are results of the stochastic nature of ice nucleation process, rather than manifestation of unknown water property.