Open Positions: Motivated and molecular simulations inclined Ph.D. and M.Sc. students always welcome!

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We shall not cease from exploration
And the end of all our exploring
Will be to arrive where we started
And know the place for the first time.

[ T. S. Eliot ]

News



July 29, 2021

The idea of using high pressure to make metal out of water is nothing new. However, the required pressure of 50 Mbar may exist in the cores of large planets, but not at terrestrial conditions. In collaboration with colleagues and friends (thank you Steve, Bernd, Robert, Tillmann, …) from the University of Southern California, the Fritz Haber Institute, the BESSY II synchrotron, and other institutes, our group (thank you Phil, Christian, Vojta, Marco,…) developed a method that allowed us to a prepare metallic water solution while completely sidestepping the need for high pressure. Inspired by work with alkali metal-liquid ammonia solutions, which at high concentrations behave like a metal, we decided to attempt formation of a conduction band not by compressing water molecules but rather by massive dissolution of electrons released from the alkali metal. In doing so, however, we had to overcome a fundamental obstacle, namely that on introduction to water, alkali metals tend to explode.

The successful way around the explosive chemistry was in exposing (inside a vacuum chamber) a drop of liquid sodium-potassium alloy to a small amount of water vapor, which began to condense on its surface. Electrons liberated from the alkali metal dissolved in the layer of water on the surface of the drop faster than the chemical reaction that results in the explosion proceeds. Moreover, there was a sufficient number of them to overcome the critical limit for the formation of a conduction band, giving thus rise to a beautiful golden metallic water solution, which we then characterized using optical reflectance and synchrotron X-ray photoelectron spectroscopies.

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Mason P.E., Schewe Ch.H., Buttersack T., Košťál V., Vitek M., McMullen R.S., Ali H., Trinter F., Lee Ch., Neumark D.M., Thürmer S., Seidel R., Winter B., Bradforth S.E., Jungwirth P.:
Spectroscopic Evidence for a Gold-Coloured Metallic Water Solution.
Nature 595: 673, 2021.


April 6, 2021

Ordinary pure water has no distinct taste, but how about heavy water – does it taste sweet, as anecdotal evidence going back to 1930s may have indicated? And if yes – why, when D2O is chemically practically identical to H2O, of which it is a stable naturally-occurring isotope? These questions arose shortly after heavy water was isolated almost 100 years ago, but they had not been satisfactorily answered until now . Together with the group of Masha Niv at the Hebrew University and Maik Behrens at the Technical University of Munich, we have now found answers to these questions using molecular dynamics simulations, cell-based experiments, mouse models, and human subjects. In our article published in Communications Biology, we show conclusively that, unlike ordinary water, heavy water tastes mildly sweet to humans but not to mice, with this effect being mediated by the human sweet taste receptor. But why does it taste sweet and not, e.g., salty or bitter, remains to be established...

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Abu N.B., Mason P.E., Klein H., Dubovski N., Shoshan-Galeczki Y.B., Malach E., Pražienková V., Maletínská L., Tempra C., Chamorro V.C., Cvačka J., Behrens M., Niv M.Y., Jungwirth P.:
Sweet taste of heavy water.
Communications Biology 4: 440, 2021.


April 1, 2021

This may look like April Fools but it's actually a serious study where we used molecular simulations with charge scaling to resolve the following puzzle - why are the experimental number densities of aqueous solutions of LiCl and NaCl practically the same at equal concentrations? Normally, one would assume that the number density of NaCl(aq) should be lower than that of LiCl(aq) since sodium cationsare larger than lithium cations. The trick is that lithium tightly orients four H2O molecules in its first solvation shell, such that these waters cannot make good hydrogen bonds with neighboring molecules. As a result, voids occur in the solvation environment of Li+ which compensate the tight first solvation shell, yielding an overall number density equal to the more regular sodium chloride solution.

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Nguyen M.T.H., Ticháček O., Martinez-Seara H., Mason P.E., Jungwirth P.:
Resolving the Equal Number Density Puzzle: Molecular Picture from Simulations of LiCl(aq) and NaCl(aq).
Journal of Physical Chemistry B 125: 3153, 2021.


August 13, 2020

JCP just published our review article where we provide a practical guide how to effectively account for electronic polarization in molecular simulations via charge scaling. Bottom line - the future of charge scaling is bright but there is a lot of work still in front of us!

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Duboué-Dijon E., Javanainen M., Delcroix P., Jungwirth P., Martinez-Seara H.:
A practical guide to biologically-relevant molecular simulations with charge scaling for electronic polarization.
Journal of Chemical Physics 153: 050901, 2020.


June 5, 2020

How is a metal formed? With colleagues from the Fritz-Haber Institute, the Berlin synchrotron BESSY II, USC Los Angeles, and Charles University in Prague we used liquid microjet photoelectron spectroscopy and ab initio molecular dynamics to map at the molecular level the electrolyte-to-metal transition in alkali metal–liquid ammonia solutions. In other words we followed in detail how the excess electrons liberated from the alkali metal change from blue localized solvated electrons to delocalized species rendering the solution a bronze-gold metallic sheen. Watching these spectacular solutions one gratefully realizes that science cane be not only exciting but also beautiful.

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Buttersack T., Mason P.E., McMullen R.S., Schewe C., Martínek T., Březina K., Crhan M., Gomez A., Hein D., Wartner G., Seidel R., Ali H., Thurmer S., Maršálek O., Winter B., Bradforth S.E., Jungwirth P.:
Photoelectron spectra of alkali metal–ammonia microjets: From blue electrolyte to bronze metal.
Science 368 (6495): 1086-1091, 2020.


April 21, 2020

pavel


April 12, 2020

Review of Scientific Instruments has published an Editorial Highlight (which they call Scilight) about our article therein. This paper summarizes our development of a refrigerated liquid ammonia microjet apparatus which we then used with our Berlin and USC colleagues to measure at the BESSY II synchrotron photoelectron spectra of alkali metal - liquid ammonia solutions (to be published - stay tuned). This is what happens if you give a theoretical group a bit of lab space...

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