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Luxembourg National Research Fund

CORE Junior: Colloidal Physics – Concerning Research on Energy Landscapes



Dr Sven Dorosz is a basic researcher: “My Junior Core Project has led to basic findings for materials research and generated numerous very good publications.” The topic that Dorosz was involved with at the University of Luxembourg is called Colloidal Physics, specifically, the ‘statistical mechanics of many-particle systems out of equilibrium’, as Dorosz explains.

What does that mean exactly Mr Dorosz?

“Liquids change, under sufficient pressure, from the liquid into the solid, crystalline phase. At the moment of phase transition – according to the laws of thermodynamics – the degree of chaos within the system, the entropy, must increase. Energy is dissipated during this process.”

The basic assumption here is that the system finds itself in a kind of equilibrium during the crystallisation process. Dorosz explains that ‘the process should be perceived in a presumably defined energy landscape.’ Within the context of the FNR Core Junior Project, his team sought to investigate the behaviour of simple liquids out of equilibrium during the phase of crystal formation:

“It was our objective to quantify the dissipated energy that is produced out of equilibrium.”

Molecules like billiard balls

In his simulations, the team concentrated on simple liquids. Physicists such as Dorosz interpret this as substances in which the molecules do not influence one another:

“One can imagine them as billiard balls that forcefully collide with one another. Other influences are not taken into consideration in the simulations.”

The physicists had to carry out an extreme quantity of statistics in order to get to the bottom of the interesting processes in the simulated liquids. Dorosz:

“Particularly those processes in the solution that are relatively atypical are interesting for comprehension of the entire system – and these can only be recorded with the aid of statistics and algorithms specially designed by us for this purpose.”

With comprehensive analysis of such atypical crystallisation processes, the scientists were then able to put together a detailed picture “of the locally released energy in the system”, Dorosz explains.

Understanding how novel materials can be obtained from a melt

A certain applicability shines through in Dorosz’s research:

“Our simulation procedures are interesting when one seeks to find out how novel materials can be obtained from a melt. We have changed many different parameters in our simulations. We learned thereby how to further improve their predictive power.”

And in the end, the research scientists were no longer forced to limit themselves only to rigid, sphere-shaped molecules; rather, they could also properly forecast the behaviour of elliptically-shaped liquid particles.

“This is an outstandingly significant finding for science”. Dorosz is pleased to say: “This was explicitly confirmed to us once again by the external reviewers during their final evaluation of my FNR Core Junior Project.”

This success story is from the 2016 FNR Annual Report. View the Annual Report as PDF or digital version

FNR Annual Report 2016 success stories