The next issue of The Journal of Physical Chemistry Letters will feature cover art from the perspective article ‘Lonely Atoms with Special Gifts: Breaking Linear Scaling Relationships in Heterogeneous Catalysis with Single-Atom Alloys’ by Matthew T. Darby, Michail Stamatakis, Angelos Michaelides, and E. Charles H. Sykes. The cover depicts the atomic structure of a so-called single-atom alloy, which is bimetallic alloy with a low concentration of the catalytically active component. One of these active sites prominently features a methane molecule after C-H bond activation. Dispersing the active component offers potential for well-defined and enhanced catalytic performance.
Posts in category Publications
The ICE group currently have two open positions for postdoctoral researchers. The positions are part of the ERC HeteroIce project aimed at understanding ice nucleation. Click here to apply or find out more information.
Andrea’s and Gerit’s paper has been published in the Proceedings of the National Academy of Sciences of the United States of America. The work had important contributions also from Jiří, a previous member of the ICE group, and from Dario and Alexandre, longstanding Angelos’ collaborators.
In the paper we study molecular crystals with quantum Monte Carlo.
Computational approaches based on the fundamental laws of quantum mechanics are now integral to almost all materials design initiatives in academia and industry. If computational materials science is genuinely going to deliver on its promises, then an electronic structure method with consistently high accuracy is urgently needed. We show that, thanks to recent algorithmic advances and the strategy developed in our manuscript, quantum Monte Carlo yields extremely accurate predictions for the lattice energies of materials at a surprisingly modest computational cost. It is thus no longer a technique that requires a world-leading computational facility to obtain meaningful results. While we focus on molecular crystals, the significance of our findings extends to all classes of materials.
Martin’s paper together with Gabriele, Fabio, Silvio and Angelos has been published in Nature Communications!
In this paper we investigate pre-critical fluctuations and what they can tell us about the heterogeneous nucleation event. Pre-critical fluctuations are the earliest occurrences of crystalline clusters in a supercooled liquid and thus readily probed in simulations such as molecular dynamics. We find that they can tell us which polymorph will form but they are not trivially indicative (as often assumed) of the nucleation enhancement. This also means that the commonly applied heterogeneous classical nucleation theory makes an error when comparing heterogeneous and homogeneous nucleation events where different polymorphs have formed. As a side, in this work we also find a simple recipe of avoiding stacking-disorder in hetergeneous ice nucleation during the nucleation stage.
Our collaborative paper with Charlie Sykes, Michail Stamatakis and other entitled “PtCu Single Atom Alloys as a Coke Resistant Strategy for Efficient C-H Activation” has been accepted for publication at Nature Chemistry. Well done everyone!
Martin’s paper together with Laurent, Ming, Gabriele, Andrea and Angelos has been published in JCP Communications! In this work we studied wetting of water droplets on a substrate. With the help of metadynamics we have uncovered that for cutoffs that are more than commonplace in the MD community (2-3 sigma) the underlying free energy profile of wetting can exhibit metastable wetting states. Those states are not only unphysical but they can also be very hard to detect and could therefore corrupt computational results and interpretations. Our results show that a cutoff should not be treated as a fitting parameter in the development of force fields since the underlying physics can be inherently different and thus one needs to use long-range versions or very large cutoffs if one wants to be absolutely sure. Read the paper online or on our publications page.
Philipp’s and Martin’s paper was published in Physical Review B! In this article they computed the ice nucleation ability of numerous model hydroxylated substrates with diverse OH group arrangements. For the substrates considered, they find that neither the symmetry of the OH patterns nor the similarity between a substrate and ice correlate well with the IN ability. Instead, they find that the OH density and the substrate-water interaction strength are useful descriptors of a material’s IN ability. This insight allows the rationalization of ice nucleation ability across a wide range of materials, and can aid the search and design of novel potent ice nucleators in the future. Check out the article online or on our publications page.
Is High-Density Amorphous Ice Simply a ‘Derailed’ State along the Ice I to Ice IV Pathway? In this paper, just accepted by The Journal of Physical Chemistry Letters, we try to answer that question by investigating a colection of high-pressure phase transitions – of ice, and ammonium fluoride as well, digging deep into the importance of the hydrogen bond network. The paper builds upon the excellent experiments of Jacob J. Shephard and Christoph G. Salzmann, topping up things with first principle simulations performed by Sanliang Ling and Ben Slater – a truly collaborative, UCL-branded work!
Andrea and Dario’s paper on the methodological improvement of the diffusion quantum Monte Carlo algorithm is finally published in Phys. Rev. B. In this work, involving also Sandro Sorella and Michael J. Gillan, we make the method up to one hundred times faster, by modifying only one line of the CASINO code. We also solve an outstanding issue of diffusion Monte Carlo, related to size-consistency, that was hampering its accuracy in many practical calculations.
It is now possible to study a whole variety of systems, including calculating interaction energies between molecules or between molecules and surfaces, or investigate the relative stability of different crystal polymorphs, with unprecedented accuracy and at a much lower computational cost.
The new method extends the range of the size of the systems that it is now possible to simulate, opening new avenues to the study of previously unaccessible problems in Nanotechnology and Material Sciences.