Publications
2022
Schmid, Michael; Parkinson, Gareth S.; Diebold, Ulrike
Analysis of Temperature-Programmed Desorption via Equilibrium Thermodynamics
Journal ArticleOpen AccessIn: ACS Physical Chemistry Au, vol. 3, iss. 1, pp. 44–62, 2022.
Abstract | Links | BibTeX | Tags: P02, P04
@article{Schmid2022,
title = {Analysis of Temperature-Programmed Desorption via Equilibrium Thermodynamics},
author = {Michael Schmid and Gareth S. Parkinson and Ulrike Diebold},
doi = {10.1021/acsphyschemau.2c00031},
year = {2022},
date = {2022-11-15},
journal = {ACS Physical Chemistry Au},
volume = {3},
issue = {1},
pages = {44--62},
publisher = {American Chemical Society (ACS)},
abstract = {Temperature-programmed desorption (TPD) experiments in surface science are usually analyzed using the Polanyi–Wigner equation and/or transition-state theory. These methods are far from straightforward, and the determination of the pre-exponential factor is often problematic. We present a different method based on equilibrium thermodynamics, which builds on an approach previously used for TPD by Kreuzer et al. (\textit{Surf. Sci.}\textbf{1988}). Equations for the desorption rate are presented for three different types of surface–adsorbate interactions: (i) a 2D ideal hard-sphere gas with a negligible diffusion barrier, (ii) an ideal lattice gas, that is, fixed adsorption sites without interaction between the adsorbates, and (iii) a lattice gas with a distribution of (site-dependent) adsorption energies. We show that the coverage dependence of the sticking coefficient for adsorption at the desorption temperature determines whether the desorption process can be described by first- or second-order kinetics. The sticking coefficient at the desorption temperature must also be known for a quantitative determination of the adsorption energy, but it has a rather weak influence (like the pre-exponential factor in a traditional TPD analysis). Quantitative analysis is also influenced by the vibrational contributions to the energy and entropy. For the case of a single adsorption energy, we provide equations to directly convert peak temperatures into adsorption energies. These equations also provide an approximation of the desorption energy in cases that cannot be described by a fixed pre-exponential factor. For the case of a distribution of adsorption energies, the desorption spectra cannot be considered a superposition of desorption spectra corresponding to the different energies. Nevertheless, we present a method to extract the distribution of adsorption energies from TPD spectra, and we rationalize the energy resolution of TPD experiments. The analytical results are complemented by a program for simulation and analysis of TPD data.},
keywords = {P02, P04},
pubstate = {published},
tppubtype = {article}
}

Zeininger, Johannes; Raab, Maximilian; Suchorski, Yuri; Buhr, Sebastian; Stöger-Pollach, Michael; Bernardi, Johannes; Rupprechter, Günther
Reaction Modes on a Single Catalytic Particle: Nanoscale Imaging and Micro-Kinetic Modeling
Journal ArticleOpen AccessIn: ACS Catalysis, vol. 12, no. 20, pp. 12774–12785, 2022.
Abstract | Links | BibTeX | Tags: P08
@article{Zeininger2022,
title = {Reaction Modes on a Single Catalytic Particle: Nanoscale Imaging and Micro-Kinetic Modeling},
author = {Johannes Zeininger and Maximilian Raab and Yuri Suchorski and Sebastian Buhr and Michael Stöger-Pollach and Johannes Bernardi and Günther Rupprechter},
doi = {10.1021/acscatal.2c02901},
year = {2022},
date = {2022-10-07},
journal = {ACS Catalysis},
volume = {12},
number = {20},
pages = {12774--12785},
publisher = {American Chemical Society (ACS)},
abstract = {The kinetic behavior of individual Rh(\textit{hkl}) nanofacets coupled in a common reaction system was studied using the apex of a curved rhodium microcrystal (radius of 0.65 μm) as a model of a single catalytic particle and field electron microscopy for in situ imaging of catalytic hydrogen oxidation. Depending on the extent of interfacet coupling via hydrogen diffusion, different oscillating reaction modes were observed including highly unusual multifrequential oscillations: differently oriented nanofacets oscillated with differing frequencies despite their immediate neighborhood. The transitions between different modes were induced by variations in the particle temperature, causing local surface reconstructions, which create locally protruding atomic rows. These atomic rows modified the coupling strength between individual nanofacets and caused the transitions between different oscillating modes. Effects such as entrainment, frequency locking, and reconstruction-induced collapse of spatial coupling were observed. To reveal the origin of the different experimentally observed effects, microkinetic simulations were performed for a network of 105 coupled oscillators, modeling the individual nanofacets communicating via hydrogen surface diffusion. The calculated behavior of the oscillators, the local frequencies, and the varying degree of spatial synchronization describe the experimental observations well.},
keywords = {P08},
pubstate = {published},
tppubtype = {article}
}

Zeininger, Johannes; Winkler, Philipp; Raab, Maximilian; Suchorski, Yuri; Prieto, Mauricio J.; Tănase, Liviu C.; Caldas, Lucas Souza; Tiwari, Aarti; Schmidt, Thomas; Stöger-Pollach, Michael; Steiger-Thirsfeld, Andreas; Cuenya, Beatriz Roldan; Rupprechter, Günther
Pattern Formation in Catalytic H2 Oxidation on Rh: Zooming in by Correlative Microscopy
Journal ArticleOpen AccessIn: ACS Catalysis, vol. 12, no. 19, pp. 11974–11983, 2022.
Abstract | Links | BibTeX | Tags: P08
@article{Zeininger2022a,
title = {Pattern Formation in Catalytic H_{2} Oxidation on Rh: Zooming in by Correlative Microscopy},
author = {Johannes Zeininger and Philipp Winkler and Maximilian Raab and Yuri Suchorski and Mauricio J. Prieto and Liviu C. Tănase and Lucas Souza Caldas and Aarti Tiwari and Thomas Schmidt and Michael Stöger-Pollach and Andreas Steiger-Thirsfeld and Beatriz Roldan Cuenya and Günther Rupprechter},
doi = {10.1021/acscatal.2c03692},
year = {2022},
date = {2022-09-19},
urldate = {2022-09-19},
journal = {ACS Catalysis},
volume = {12},
number = {19},
pages = {11974--11983},
publisher = {American Chemical Society (ACS)},
abstract = {Spatio-temporal nonuniformities in H_{2} oxidation on individual Rh(\textit{h k l}) domains of a polycrystalline Rh foil were studied in the 10^{–6} mbar pressure range by photoemission electron microscopy (PEEM), X-ray photoemission electron microscopy (XPEEM), and low-energy electron microscopy (LEEM). The latter two were used for in situ correlative microscopy to zoom in with significantly higher lateral resolution, allowing detection of an unusual island-mediated oxygen front propagation during kinetic transitions. The origin of the island-mediated front propagation was rationalized by model calculations based on a hybrid approach of microkinetic modeling and Monte Carlo simulations.},
keywords = {P08},
pubstate = {published},
tppubtype = {article}
}

Tröster, Andreas; Verdi, Carla; Dellago, Christoph; Rychetsky, Ivan; Kresse, Georg; Schranz, Wilfried
Hard antiphase domain boundaries in strontium titanate unravelled using machine-learned force fields
Journal ArticleIn: Physical Review Materials, vol. 6, no. 9, pp. 094408, 2022.
Abstract | Links | BibTeX | Tags: P03, P12
@article{Troester2022,
title = {Hard antiphase domain boundaries in strontium titanate unravelled using machine-learned force fields},
author = {Andreas Tröster and Carla Verdi and Christoph Dellago and Ivan Rychetsky and Georg Kresse and Wilfried Schranz},
doi = {10.1103/physrevmaterials.6.094408},
year = {2022},
date = {2022-09-16},
urldate = {2022-09-16},
journal = {Physical Review Materials},
volume = {6},
number = {9},
pages = {094408},
publisher = {American Physical Society (APS)},
abstract = {We investigate the properties of hard antiphase boundaries in SrTiO_{3} using machine-learned force fields. In contrast to earlier findings based on standard \textit{ab initio} methods, for all pressures up to 120kbar the observed domain wall pattern maintains an almost perfect Néel character in quantitative agreement with Landau-Ginzburg-Devonshire theory, and the in-plane polarization P_{3} shows no tendency to decay to zero. Together with the switching properties of P_{3} under reversal of the Néel order parameter component, this provides hard evidence for the presence of rotopolar couplings. The present approach overcomes the severe limitations of \textit{ab initio} simulations of wide domain walls and opens avenues toward concise atomistic predictions of domain-wall properties even at finite temperatures.},
keywords = {P03, P12},
pubstate = {published},
tppubtype = {article}
}

Wanzenböck, Ralf; Arrigoni, Marco; Bichelmaier, Sebastian; Buchner, Florian; Carrete, Jesús; Madsen, Georg K. H.
Neural-network-backed evolutionary search for SrTiO3(110) surface reconstructions
Journal ArticleOpen AccessIn: Digital Discovery, vol. 1, no. 5, pp. 703–710, 2022.
Abstract | Links | BibTeX | Tags: P09
@article{Wanzenboeck2022,
title = {Neural-network-backed evolutionary search for SrTiO_{3}(110) surface reconstructions},
author = {Ralf Wanzenböck and Marco Arrigoni and Sebastian Bichelmaier and Florian Buchner and Jesús Carrete and Georg K. H. Madsen},
doi = {10.1039/d2dd00072e},
year = {2022},
date = {2022-08-26},
journal = {Digital Discovery},
volume = {1},
number = {5},
pages = {703--710},
publisher = {Royal Society of Chemistry (RSC)},
abstract = {The determination of atomic structures in surface reconstructions has typically relied on structural models derived from intuition and domain knowledge. Evolutionary algorithms have emerged as powerful tools for such structure searches. However, when density functional theory is used to evaluate the energy the computational cost of a thorough exploration of the potential energy landscape is prohibitive. Here, we drive the exploration of the rich phase diagram of TiO_{x} overlayer structures on SrTiO_{3}(110) by combining the covariance matrix adaptation evolution strategy (CMA-ES) and a neural-network force field (NNFF) as a surrogate energy model. By training solely on SrTiO_{3}(110) 4×1 overlayer structures and performing CMA-ES runs on 3×1, 4×1 and 5×1 overlayers, we verify the transferability of the NNFF. The speedup due to the surrogate model allows taking advantage of the stochastic nature of the CMA-ES to perform exhaustive sets of explorations and identify both known and new low-energy reconstructions.},
keywords = {P09},
pubstate = {published},
tppubtype = {article}
}
Tampieri, Alberto; Föttinger, Karin; Barrabés, Noelia; Medina, Francesc
Journal ArticleOpen AccessIn: Applied Catalysis B: Environmental, vol. 319, no. 121889, 2022.
Abstract | Links | BibTeX | Tags: P10
@article{TAMPIERI2022121889,
title = {Catalytic aldol condensation of bio-derived furanic aldehydes and acetone: Challenges and opportunities},
author = {Alberto Tampieri and Karin Föttinger and Noelia Barrabés and Francesc Medina},
url = {https://doi.org/10.1016/j.apcatb.2022.121889
https://www.sciencedirect.com/science/article/pii/S092633732200830X},
doi = {10.1016/j.apcatb.2022.121889},
year = {2022},
date = {2022-08-24},
urldate = {2022-08-24},
journal = {Applied Catalysis B: Environmental},
volume = {319},
number = {121889},
abstract = {Bio-derived furfural and 5-hydroxymethylfurfural can be combined with acetone to yield aldol condensation products that may serve as biofuel and polymer precursors. We have explored different catalytic systems to obtain and purify each product in the most efficient way. The results of the catalytic tests of the cross-condensations and of the self-condensation of acetone allowed the comparison of the different reactivity of the two aldehydes. Online and in situ/operando ATR-IR was used to monitor the reaction over time and to study the interaction of the reaction species with the solid catalyst, especially the formation of deactivating organic matter that covers the surface, which is a major issue in heterogeneous condensation processes. In situ NMR was used to study the ongoing reaction, assessing its stereoselectivity, and to study the behavior of deuterated species in the catalytic system. Finally, the preparation of C14, a hetero-double-condensation product, was also explored.},
keywords = {P10},
pubstate = {published},
tppubtype = {article}
}

Coretti, Alessandro; Falkner, Sebastian; Geissler, Phillip; Dellago, Christoph
Learning Mappings between Equilibrium States of Liquid Systems Using Normalizing Flows
Journal ArticleOpen AccessarXivIn: arXiv, 2022.
Abstract | Links | BibTeX | Tags: P12
@article{Coretti2022,
title = {Learning Mappings between Equilibrium States of Liquid Systems Using Normalizing Flows},
author = {Alessandro Coretti and Sebastian Falkner and Phillip Geissler and Christoph Dellago},
url = {https://arxiv.org/abs/2208.10420},
year = {2022},
date = {2022-08-22},
urldate = {2022-08-22},
journal = {arXiv},
abstract = { Generative models are a promising tool to address the sampling problem in multi-body and condensed-matter systems in the framework of statistical mechanics. In this work, we show that normalizing flows can be used to learn a transformation to map different liquid systems into each other allowing at the same time to obtain an unbiased equilibrium distribution through a reweighting process. Two proof-of-principles calculations are presented for the transformation between Lennard-Jones systems of particles with different depths of the potential well and for the transformation between a Lennard-Jones and a system of repulsive particles. In both numerical experiments, systems are in the liquid state. In future applications, this approach could lead to efficient methods to simulate liquid systems at ab-initio accuracy with the computational cost of less accurate models, such as force field or coarse-grained simulations.},
keywords = {P12},
pubstate = {published},
tppubtype = {article}
}

Wang, Zhichang; Reticcioli, Michele; Jakub, Zdenek; Sokolović, Igor; Meier, Matthias; Boatner, Lynn A; Schmid, Michael; Parkinson, Gareth S.; Diebold, Ulrike; Franchini, Cesare; Setvin, Martin
Surface chemistry on a polarizable surface: Coupling of CO with KTaO 3(001)
Journal ArticleOpen AccessIn: Science Advances, vol. 8, iss. 33, 2022.
Abstract | Links | BibTeX | Tags: P02, P04, P07
@article{Wang2022,
title = {Surface chemistry on a polarizable surface: Coupling of CO with KTaO _{3}(001)},
author = {Zhichang Wang and Michele Reticcioli and Zdenek Jakub and Igor Sokolović and Matthias Meier and Lynn A Boatner and Michael Schmid and Gareth S. Parkinson and Ulrike Diebold and Cesare Franchini and Martin Setvin},
url = {https://www.science.org/doi/10.1126/sciadv.abq1433},
doi = {10.1126/sciadv.abq1433},
year = {2022},
date = {2022-08-19},
urldate = {2022-08-19},
journal = {Science Advances},
volume = {8},
issue = {33},
publisher = {American Association for the Advancement of Science (AAAS)},
abstract = {Polarizable materials attract attention in catalysis because they have a free parameter for tuning chemical reactivity. Their surfaces entangle the dielectric polarization with surface polarity, excess charge, and orbital hybridization. How this affects individual adsorbed molecules is shown for the incipient ferroelectric perovskite KTaO_{3}. This intrinsically polar material cleaves along (001) into KO- and TaO_{2}-terminated surface domains. At TaO_{2} terraces, the polarity-compensating excess electrons form a two-dimensional electron gas and can also localize by coupling to ferroelectric distortions. TaO_{2} terraces host two distinct types of CO molecules, adsorbed at equivalent lattice sites but charged differently as seen in atomic force microscopy/scanning tunneling microscopy. Temperature-programmed desorption shows substantially stronger binding of the charged CO; in density functional theory calculations, the excess charge favors a bipolaronic configuration coupled to the CO. These results pinpoint how adsorption states couple to ferroelectric polarization.},
keywords = {P02, P04, P07},
pubstate = {published},
tppubtype = {article}
}

Reticcioli, Michele; Wang, Zhichang; Schmid, Michael; Wrana, Dominik; Boatner, Lynn A.; Diebold, Ulrike; Setvin, Martin; Franchini, Cesare
Competing electronic states emerging on polar surfaces
Journal ArticleOpen AccessIn: Nature Communications, vol. 13, no. 4311, 2022.
Abstract | Links | BibTeX | Tags: P02, P07
@article{Reticcioli2022,
title = {Competing electronic states emerging on polar surfaces},
author = {Michele Reticcioli and Zhichang Wang and Michael Schmid and Dominik Wrana and Lynn A. Boatner and Ulrike Diebold and Martin Setvin and Cesare Franchini},
url = {https://www.nature.com/articles/s41467-022-31953-6},
doi = {10.1038/s41467-022-31953-6},
year = {2022},
date = {2022-07-25},
urldate = {2022-07-25},
journal = {Nature Communications},
volume = {13},
number = {4311},
publisher = {Springer Science and Business Media LLC},
abstract = {Excess charge on polar surfaces of ionic compounds is commonly described by the two-dimensional electron gas (2DEG) model, a homogeneous distribution of charge, spatially-confined in a few atomic layers. Here, by combining scanning probe microscopy with density functional theory calculations, we show that excess charge on the polar TaO_{2} termination of KTaO_{3}(001) forms more complex electronic states with different degrees of spatial and electronic localization: charge density waves (CDW) coexist with strongly-localized electron polarons and bipolarons. These surface electronic reconstructions, originating from the combined action of electron-lattice interaction and electronic correlation, are energetically more favorable than the 2DEG solution. They exhibit distinct spectroscopy signals and impact on the surface properties, as manifested by a local suppression of ferroelectric distortions.},
keywords = {P02, P07},
pubstate = {published},
tppubtype = {article}
}
![Role of Polarons in Single-Atom Catalysts: Case Study of Me1[Au1,Pt1 and Rh1] on TiO2(110)](https://sfb-taco.at/wp-content/uploads/2023/02/P07_P04-300x300.png)
Sombut, Panukorn; Puntscher, Lena; Atzmüller, Marlene; Jakub, Zdenek; Reticcioli, Michele; Meier, Matthias; Parkinson, Gareth S.; Franchini, Cesare
Role of Polarons in Single-Atom Catalysts: Case Study of Me1[Au1,Pt1 and Rh1] on TiO2(110)
Journal ArticleOpen AccessIn: Topics in Catalysis, vol. 65, pp. 1620–1630, 2022.
Abstract | Links | BibTeX | Tags: P04, P07
@article{Sombut2022,
title = {Role of Polarons in Single-Atom Catalysts: Case Study of Me_{1}[Au_{1},Pt_{1} and Rh_{1}] on TiO_{2}(110)},
author = {Panukorn Sombut and Lena Puntscher and Marlene Atzmüller and Zdenek Jakub and Michele Reticcioli and Matthias Meier and Gareth S. Parkinson and Cesare Franchini},
doi = {10.1007/s11244-022-01651-0},
year = {2022},
date = {2022-07-25},
journal = {Topics in Catalysis},
volume = {65},
pages = {1620--1630},
abstract = {The local environment of metal-oxide supported single-atom catalysts plays a decisive role in the surface reactivity and related catalytic properties. The study of such systems is complicated by the presence of point defects on the surface, which are often associated with the localization of excess charge in the form of polarons. This can affect the stability, the electronic configuration, and the local geometry of the adsorbed adatoms. In this work, through the use of density functional theory and surface-sensitive experiments, we study the adsorption of Rh_{1}, Pt_{1}, and Au_{1} metals on the reduced TiO_{2}(110) surface, a prototypical polaronic material. A systematic analysis of the adsorption configurations and oxidation states of the adsorbed metals reveals different types of couplings between adsorbates and polarons. As confirmed by scanning tunneling microscopy measurements, the favored Pt_{1} and Au_{1} adsorption at oxygen vacancy sites is associated with a strong electronic charge transfer from polaronic states to adatom orbitals, which results in a reduction of the adsorbed metal. In contrast, the Rh_{1} adatoms interact weakly with the excess charge, which leaves the polarons largely unaffected. Our results show that an accurate understanding of the properties of single-atom catalysts on oxide surfaces requires a careful account of the interplay between adatoms, vacancy sites, and polarons.},
keywords = {P04, P07},
pubstate = {published},
tppubtype = {article}
}