Nav: Home

Theoretical physicists unveil one of the most ubiquitous and elusive concepts in chemistry

July 01, 2019

Even if we study them at school, oxidation numbers have so far eluded any rigorous quantum mechanical definition. A new SISSA study, published in Nature Physics, reverses this state of affairs by providing such a definition, based on the theory of topological quantum numbers, which was honoured with the 2016 Nobel prize in Physics awarded to Thouless, Haldane and Kosterlitz. This result, combined with recent advances in the theory of transport achieved at SISSA, paves the way to an accurate, yet tractable, numerical simulation of a broad class of materials that are important in energy-related technologies and planetary sciences.

Every undergraduate student in the natural sciences learns how to associate an integer oxidation number to a chemical species participating in a reaction. Unfortunately, the very concept of oxidation state has thus far eluded a rigorous quantum mechanical definition, so that no method was known until now to compute oxidation numbers from the fundamental laws of nature, let alone demonstrate that their use in the simulation of charge transport does not spoil the quality of numerical simulations. At the same time, the evaluation of electric currents in ionic conductors, which is required to model their transport properties, is presently based on a cumbersome quantum-mechanical approach that severely limits the feasibility of large-scale computer simulations. Scientists have lately noticed that a simplified model where each atom carries a charge equal to its oxidation number may give results in surprising good agreement with rigorous but much more expensive approaches. By combining the new topological definition of oxidation number with the so-called "gauge invariance" of transport coefficients, recently discovered at SISSA, Federico Grasselli and Stefano Baroni proved that what was considered a mere coincidence stands in fact on solid theoretical grounds, and that the simple integer-charge model captures the electrical transport properties of ionic conductors without any approximations.

Besides solving a fundamental conundrum in condensed matter physics, this result, achieved within the framework of the European MAX Centre of Excellence for supercomputing applications, also represents a breakthrough for applications, enabling computationally feasible quantum simulations of charge transport in ionic systems of paramount importance in energy-related technologies, in the automotive and telecommunications sectors, as well as in planetary sciences. Such applications range from the ionic mixtures adopted in electrolytic cells and heat exchangers in power plants, to solid-state-electrolyte batteries for electric cars and electronic devices, and even to the conducting exotic phases of water occurring in the interior of icy giants, which are supposed to be related to the origin of the magnetic fields in these planets.
-end-


Scuola Internazionale Superiore di Studi Avanzati

Related Planetary Sciences Articles:

Planetary collisions can drop the internal pressures in planets
A new study finds that collisions between planetary bodies, such as the event that created Earth's moon, could abruptly drop the planet's internal pressure.
When it comes to planetary habitability, it's what's inside that counts
Which of Earth's features were essential for the origin and sustenance of life?
Massive collision in the planetary system Kepler 107
Two of the planets which are orbiting the star Kepler 107 could be the result of an impact similar to that which affected the Earth to produce the moon.
ASU scientists study organization of life on a planetary scale
In astrobiology, there is an increasing interest in whether life as we know it is a quirk of the particular evolutionary history of the Earth or, instead, if life might be governed by more general organizing principles.
Planetary collision that formed the moon made life possible on Earth
Most of Earth's life-essential elements probably arrived with the planetary collision that produced the moon.
Planetary boundaries for antibiotic and pesticide resistance identified
Researchers have now published the first estimates of antibiotic and pesticide 'planetary boundaries' in the journal Nature Sustainability.
Some planetary systems just aren't into heavy metal
Small planetary systems with multiple planets are not fans of heavy metal -- think iron, not Iron Maiden -- according to a new Yale University study.
Ultra-close stars discovered inside a planetary nebula
An international team of astronomers have discovered two stars in a binary pair that complete an orbit around each other in a little over three hours, residing in the planetary nebula M3-1.
Feeding 10 billion people by 2050 within planetary limits may be achievable
The study is the first to quantify how food production and consumption affects the planetary boundaries that describe a safe operating space for humanity beyond which Earth's vital systems could become unstable.
The only known white dwarf orbited by planetary fragments has been analyzed
The study, led by Paula Izquierdo, a doctoral student at the Instituto de Astrofísica de Canarias (IAC) and the University of La Laguna (ULL), has gone deeply into the analysis of this exceptional white dwarf, which shows periodic transits produced by fragments of a shredded planetesimal.
More Planetary Sciences News and Planetary Sciences Current Events

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Rethinking Anger
Anger is universal and complex: it can be quiet, festering, justified, vengeful, and destructive. This hour, TED speakers explore the many sides of anger, why we need it, and who's allowed to feel it. Guests include psychologists Ryan Martin and Russell Kolts, writer Soraya Chemaly, former talk radio host Lisa Fritsch, and business professor Dan Moshavi.
Now Playing: Science for the People

#538 Nobels and Astrophysics
This week we start with this year's physics Nobel Prize awarded to Jim Peebles, Michel Mayor, and Didier Queloz and finish with a discussion of the Nobel Prizes as a way to award and highlight important science. Are they still relevant? When science breakthroughs are built on the backs of hundreds -- and sometimes thousands -- of people's hard work, how do you pick just three to highlight? Join host Rachelle Saunders and astrophysicist, author, and science communicator Ethan Siegel for their chat about astrophysics and Nobel Prizes.