It was one of the “missing pieces” in the Theoretical Physics of Materials puzzle and researchers have finally found it. The study will allow scientists to simulate this phenomenon numerically in extreme temperature and pressure conditions, eg those existing inside planets, or for materials, such as covalent glasses or liquids, to which current methods do not apply.
Although well known and extensively studied, so far it has never been given a theoretical description taking into account both the behaviour of atoms – regulated by the laws of classical mechanics – and the behaviour of electrons, which instead follows the laws of quantum mechanics. “This has prevented scientists from applying powerful numerical simulation methods… to thermal transport in many technologically and scientifically highly interesting systems.” said Prof Baroni.
“In order to predict the thermal behaviour of materials, we have so far had to use ‘approximate methods’, which have been successfully applied to many of these technological problems,” continues Baroni. “However, these methods suffer some severe limitations when it comes to applying them to covalent glasses and liquids or to materials in extreme pressure and temperature conditions, such as those existing inside planets.” In fact, these conditions – the scientist explains – are so extreme that they cannot be reproduced in the laboratory, and numerical simulation is the only possibility for understanding the heat dissipation mechanisms of planets, an essential element for learning about their composition and internal structure.
“To devise a general method for simulating thermal transport processes, scientists were lacking a theoretical framework, which our study has finally provided,” explains Baroni. “Our method is accurate and general, but it requires massive computational resources.” Ulysses, the supercomputing system recently acquired by SISSA, will prove precious in this respect. For more ambitious applications we’ll have to use the supercomputers eg CINECA in Bologna, and sophisticated software techniques, eg MaX (“Materials at the eXascale”).
Have you ever wondered why, when you leave your car in the sun, you get burnt if you touch the car body but not if you touch the seats? The two materials making up the car body and seats are at the same temperature, and yet when you touch them they give completely different sensations. “The property that changes between metal and fabric is thermal conduction, the thermal equivalent of electrical conduction,” explains Baroni. “The metal car body has a much higher conductivity than fabric and so it is much more efficient at transmitting its heat to bodies that come into contact with it (our hand).” http://www.nature.com/nphys/journal/vaop/ncurrent/full/nphys3509.html http://www.alphagalileo.org/ViewItem.aspx?ItemId=157457&CultureCode=en
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