Supercomputer simulation of ice formation gives evidence of ‘Mpemba effect’

• Researchers from Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), an autonomous institute of the Department of Science and Technology (DST), have developed the first supercomputer-powered simulations to capture evidence on ‘Mpemba effect’.

What is Mpemba effect?

• A hotter sample of water may freeze faster, than a colder one, when kept inside a refrigerator working at a sub-freezing temperature. 

• This counterintuitive fact is now referred to as the ‘Mpemba effect’ and discussed since the time of Aristotle.

• The phenomenon forgotten over time was rediscovered in the last century by Erasto Mpemba after whom it is now named.

• Since then, there has been considerable interest in understanding it and identifying whether the effect is specific only to phase transitions in water. 

• Even though it is recently shown that the effect appears during phase transitions in several other systems, the understanding remains largely elusive. 

• Furthermore, quite interestingly, the case of water has recently become controversial, even at the experimental level. 

Highlights of the new study:

• The researchers used supercomputers to develop the first simulation of ice formation proving the ‘Mpemba effect’ of water and also demonstrating that it can appear during fluid-to-solid transitions in systems other than water.

• They have explained that when water cools, it can get stuck in intermediate states of short-lived molecular arrangements before true ice begins to grow. 

• Different starting temperatures get stuck for varied lengths of time.

• Hotter water can sometimes “choose” a quicker path to nucleation, the birth of ice, bypassing the delays that colder water suffers.

• The best explanation yet of why “hot can freeze faster than cold” is one major step into the world of non-equilibrium physics.

• This research published in the journal Communication Physics can provide new insights into phenomena such as relaxation of materials due to sudden temperature changes technically called out-of-equilibrium phenomena and also can lead to diverse applications, such as giving a new perspective to thermal control in next generation electronics or defining better cooling strategies.

(The author is a trainer for Civil Services aspirants.)