Publications
2022

Kiatsaengthong, Danusorn; Jaroenpanon, Kanticha; Somchuea, Pooripong; Chukeaw, Thanaphat; Chareonpanich, Metta; Faungnawakij, Kajornsak; Sohn, Hiesang; Rupprechter, Günther; Seubsai, Anusorn
Journal ArticleOpen AccessIn: ACS Omega, vol. 7, no. 2, pp. 1785–1793, 2022.
Abstract | Links | BibTeX | Tags: P08
@article{Kiatsaengthong2022,
title = {Effects of Mg, Ca, Sr, and Ba Dopants on the Performance of La_{2}O_{3} Catalysts for the Oxidative Coupling of Methane},
author = {Danusorn Kiatsaengthong and Kanticha Jaroenpanon and Pooripong Somchuea and Thanaphat Chukeaw and Metta Chareonpanich and Kajornsak Faungnawakij and Hiesang Sohn and Günther Rupprechter and Anusorn Seubsai},
doi = {10.1021/acsomega.1c04738},
year = {2022},
date = {2022-01-04},
urldate = {2022-01-04},
journal = {ACS Omega},
volume = {7},
number = {2},
pages = {1785--1793},
publisher = {American Chemical Society (ACS)},
abstract = {Oxidative coupling of methane (OCM) is a reaction to directly convert methane into high value-added hydrocarbons (C_{2+}) such as ethylene and ethane using molecular oxygen and a catalyst. This work investigated lanthanum oxide catalysts for OCM, which were promoted with alkaline-earth metal oxides (Mg, Ca, Sr, and Ba) and prepared by the solution-mixing method. The synthesized catalysts were characterized using X-ray powder diffraction, CO_{2}-programmed desorption, and X-ray photoelectron spectroscopy. The comparative performance of each promoter showed that promising lanthanum-loaded alkaline-earth metal oxide catalysts were La-Sr and La-Ba. In contrast, the combination of La with Ca or Mg did not lead to a clear improvement of C_{2+} yield. The most promising LaSr50 catalyst exhibited the highest C_{2+} yield of 17.2%, with a 56.0% C_{2+} selectivity and a 30.9% CH_{4} conversion. Catalyst characterization indicated that their activity was strongly associated with moderate basic sites and surface-adsorbed oxygen species of O_{2}^{–}. Moreover, the catalyst was stable over 25 h at a reactor temperature of 700 °C.},
keywords = {P08},
pubstate = {published},
tppubtype = {article}
}

Montes-Campos, Hadrián; Carrete, Jesús; Bichelmaier, Sebastian; Varela, Luis M; Madsen, Georg K. H.
A Differentiable Neural-Network Force Field for Ionic Liquids
Journal ArticleOpen AccessIn: Journal of Chemical Information and Modeling, vol. 62, no. 1, pp. 88–101, 2022.
Abstract | Links | BibTeX | Tags: P09
@article{MontesCampos2021,
title = {A Differentiable Neural-Network Force Field for Ionic Liquids},
author = {Hadrián Montes-Campos and Jesús Carrete and Sebastian Bichelmaier and Luis M Varela and Georg K. H. Madsen},
doi = {10.1021/acs.jcim.1c01380},
year = {2022},
date = {2022-01-03},
urldate = {2022-01-03},
journal = {Journal of Chemical Information and Modeling},
volume = {62},
number = {1},
pages = {88--101},
abstract = {We present NeuralIL, a model for the potential energy of an ionic liquid that accurately reproduces first-principles results with orders-of-magnitude savings in computational cost. Based on a multilayer perceptron and spherical Bessel descriptors of the atomic environments, NeuralIL is implemented in such a way as to be fully automatically differentiable. It can thus be trained on ab-initio forces instead of just energies, to make the most out of the available data, and can efficiently predict arbitrary derivatives of the potential energy. We parametrize the model for the case of ethylammonium nitrate. We discuss the best way to include chemical information in the atom-centered descriptors for a many-component system. Furthermore, we demonstrate an ensemble-learning approach to the detection of extrapolation. With out-of-sample accuracies better than 0.1 kcal/mol in the energies and 100 meV/Å in the forces, our potential model considerably outperforms molecular-mechanics force fields and opens the door to large-scale thermodynamical calculations with ab-initio-like accuracy for ionic liquids. Including the forces does away with the idea that vast amounts of atomic configurations are required to train a neural network force field based on atom-centered descriptors. We also find that a separate treatment of long-range interactions is not required to achieve a high-quality representation of the potential
energy surface of these dense ionic systems.},
keywords = {P09},
pubstate = {published},
tppubtype = {article}
}
energy surface of these dense ionic systems.
2021

Pramhaas, Verena; Rupprechter, Günther
Book ChapterIn: Ambient Pressure Spectroscopy in Complex Chemical Environments, vol. 1396, Chapter 6, pp. 119–145, American Chemical Society, 2021, ISBN: 9780841298125.
Abstract | Links | BibTeX | Tags: P08
@inbook{Pramhaas2021,
title = {Sum Frequency Generation in Ambient Environments: Vibrational Spectroscopy at Solid/Gas and Solid/Liquid Interfaces},
author = {Verena Pramhaas and Günther Rupprechter},
doi = {10.1021/bk-2021-1396.ch006},
isbn = {9780841298125},
year = {2021},
date = {2021-11-11},
booktitle = {Ambient Pressure Spectroscopy in Complex Chemical Environments},
journal = {ACS Symposium Series},
volume = {1396},
pages = {119--145},
publisher = {American Chemical Society},
chapter = {6},
abstract = {Molecules at solid/gas and solid/liquid interfaces are key players in many fields of technology, such as adsorption, corrosion, catalysis, electrochemistry and tribology. Their characterization is challenging, as they are “buried” under bulk phases. Due to its interface-specificity, nonlinear optical infrared-visible sum frequency generation (SFG) laser spectroscopy is an ideal method for their characterization, providing vibrational spectra of exclusively interfacial molecules. SFG also yields information on molecular structure, symmetry and orientation (tilt angle) and can be carried out with sub-picosecond time resolution. We introduce the SFG basics and instrumentation, and discuss exemplary studies chosen from recent research of gas adsorption on solid surfaces, as well as of increasingly complex molecules at solid/gas and solid/liquid interfaces.},
keywords = {P08},
pubstate = {published},
tppubtype = {inbook}
}
Jakub, Zdenek; Meier, Matthias; Kraushofer, Florian; Balajka, Jan; Pavelec, Jiri; Schmid, Michael; Franchini, Cesare; Diebold, Ulrike; Parkinson, Gareth S.
Rapid oxygen exchange between hematite and water vapor
Journal ArticleOpen AccessIn: Nature Communications, vol. 12, iss. 1, no. 6488, 2021.
Abstract | Links | BibTeX | Tags: P02, P04, P07
@article{Jakub2021,
title = {Rapid oxygen exchange between hematite and water vapor},
author = {Zdenek Jakub and Matthias Meier and Florian Kraushofer and Jan Balajka and Jiri Pavelec and Michael Schmid and Cesare Franchini and Ulrike Diebold and Gareth S. Parkinson},
doi = {10.1038/s41467-021-26601-4},
year = {2021},
date = {2021-11-10},
journal = {Nature Communications},
volume = {12},
number = {6488},
issue = {1},
publisher = {Springer Science and Business Media LLC},
abstract = {Oxygen exchange at oxide/liquid and oxide/gas interfaces is important in technology and environmental studies, as it is closely linked to both catalytic activity and material degradation. The atomic-scale details are mostly unknown, however, and are often ascribed to poorly defined defects in the crystal lattice. Here we show that even thermodynamically stable, well-ordered surfaces can be surprisingly reactive. Specifically, we show that all the 3-fold coordinated lattice oxygen atoms on a defect-free single-crystalline “r-cut” (1-102) surface of hematite (α-Fe_{2}O_{3}) are exchanged with oxygen from surrounding water vapor within minutes at temperatures below 70 °C, while the atomic-scale surface structure is unperturbed by the process. A similar behavior is observed after liquid-water exposure, but the experimental data clearly show most of the exchange happens during desorption of the final monolayer, not during immersion. Density functional theory computations show that the exchange can happen during on-surface diffusion, where the cost of the lattice oxygen extraction is compensated by the stability of an HO-HOH-OH complex. Such insights into lattice oxygen stability are highly relevant for many research fields ranging from catalysis and hydrogen production to geochemistry and paleoclimatology.},
keywords = {P02, P04, P07},
pubstate = {published},
tppubtype = {article}
}

Haunold, Thomas; Rupprechter, Günther
LiOx-modification of Ni and Co3O4 surfaces: An XPS, LEIS and LEED study
Journal ArticleOpen AccessIn: Surface Science, vol. 713, pp. 121915, 2021.
Abstract | Links | BibTeX | Tags: P08
@article{Haunold2021,
title = {LiOx-modification of Ni and Co_{3}O_{4} surfaces: An XPS, LEIS and LEED study},
author = {Thomas Haunold and Günther Rupprechter},
doi = {10.1016/j.susc.2021.121915},
year = {2021},
date = {2021-11-01},
urldate = {2021-11-01},
journal = {Surface Science},
volume = {713},
pages = {121915},
publisher = {Elsevier BV},
abstract = {LiO_{x} was deposited at room temperature by physical vapor deposition (PVD) on polycrystalline Ni foil and Co_{3}O_{4}(111) thin film, creating uniform model systems well-suited for surface-sensitive characterization by X-ray photoelectron spectroscopy (XPS), low energy ion scattering (LEIS) or low energy electron diffraction (LEED). In the case of Ni, about 15 layers of LiO_{x} film were grown under the current conditions either stepwise or continuously, with XPS analysis indicating a deposition rate of 0.16 and 0.24 ML/min, respectively. Li 1s and O 1s spectra revealed that Li_{2}O and to a lesser extent LiOH were preferentially formed. The stability of the LiO_{x}films was examined in UHV, upon annealing at 573 K and upon hydrogen reduction at 723 K. On the more reactive Co_{3}O_{4}(111) film grown on Ir(100), the Li accommodation rate was about twice as high, at least within the first minutes of deposition. Post-deposition LEED showed an obscured cobalt oxide diffraction pattern, not unexpected in light of the LiO_{x} deposited. On both substrates, LEIS characterization of Li (≈ 103 eV) was prevented by the high background in this kinetic energy region, due to surface roughness and unspecific scattering. Still, LiO_{x} deposition was evident from the vanished LEIS signals of Ni or Co. The prepared LiO_{x}-modified surfaces may serve as starting point for the future growth of epitaxial Li_{x}CoO_{2} model systems.},
keywords = {P08},
pubstate = {published},
tppubtype = {article}
}

Verdi, Carla; Karsai, Ferenc; Liu, Peitao; Jinnouchi, Ryosuke; Kresse, Georg
Journal ArticleOpen AccessIn: npj Computational Materials, vol. 7, pp. 156, 2021.
Abstract | Links | BibTeX | Tags: P03
@article{Verdi2021,
title = {Thermal transport and phase transitions of zirconia by on-the-fly machine-learned interatomic potentials},
author = {Carla Verdi and Ferenc Karsai and Peitao Liu and Ryosuke Jinnouchi and Georg Kresse},
doi = {10.1038/s41524-021-00630-5},
year = {2021},
date = {2021-09-30},
urldate = {2021-09-30},
journal = {npj Computational Materials},
volume = {7},
pages = {156},
publisher = {Springer Science and Business Media LLC},
abstract = {Machine-learned interatomic potentials enable realistic finite temperature calculations of complex materials properties with first-principles accuracy. It is not yet clear, however, how accurately they describe anharmonic properties, which are crucial for predicting the lattice thermal conductivity and phase transitions in solids and, thus, shape their technological applications. Here we employ a recently developed on-the-fly learning technique based on molecular dynamics and Bayesian inference in order to generate an interatomic potential capable to describe the thermodynamic properties of zirconia, an important transition metal oxide. This machine-learned potential accurately captures the temperature-induced phase transitions below the melting point. We further showcase the predictive power of the potential by calculating the heat transport on the basis of Green–Kubo theory, which allows to account for anharmonic effects to all orders. This study indicates that machine-learned potentials trained on the fly offer a routine solution for accurate and efficient simulations of the thermodynamic properties of a vast class of anharmonic materials.},
keywords = {P03},
pubstate = {published},
tppubtype = {article}
}

Franceschi, Giada; Schmid, Michael; Diebold, Ulrike; Riva, Michele
Two-dimensional surface phase diagram of a multicomponent perovskite oxide: La0.8Sr0.2MnO3 (110)
Journal ArticleIn: Physical Review Materials, vol. 5, no. 9, pp. L092401, 2021.
Abstract | Links | BibTeX | Tags: P02
@article{Franceschi2021,
title = {Two-dimensional surface phase diagram of a multicomponent perovskite oxide: La_{0.8}Sr_{0.2}MnO_{3} (110)},
author = {Giada Franceschi and Michael Schmid and Ulrike Diebold and Michele Riva},
doi = {10.1103/physrevmaterials.5.l092401},
year = {2021},
date = {2021-09-24},
urldate = {2021-09-24},
journal = {Physical Review Materials},
volume = {5},
number = {9},
pages = {L092401},
publisher = {American Physical Society (APS)},
abstract = {The many surface reconstructions of (110)-oriented lanthanum strontium manganite (\textbf{La_{0.8}Sr_{0.2}MnO}3}}, LSMO) were followed as a function of the oxygen chemical potential (\textit{\textbf{μ}_{O}}) and the surface cation composition. Decreasing \textit{\textbf{μ}_{O}} causes Mn to migrate across the surface, enforcing phase separation into \textit{\textbf{A}}-site-rich areas and a variety of composition-related, structurally diverse \textit{\textbf{B}}-site-rich reconstructions. The composition of these phase-separated structures was quantified with scanning tunneling microscopy, and these results were used to build a two-dimensional phase diagram of the LSMO(110) equilibrium surface structures.},
keywords = {P02},
pubstate = {published},
tppubtype = {article}
}

Zeininger, Johannes; Suchorski, Yuri; Raab, Maximilian; Buhr, Sebastian; Grönbeck, Henrik; Rupprechter, Günther
Single-Particle Catalysis: Revealing Intraparticle Pacemakers in Catalytic H2 Oxidation on Rh
Journal ArticleOpen AccessIn: ACS Catalysis, vol. 11, no. 15, pp. 10020–10027, 2021.
Abstract | Links | BibTeX | Tags: P08, TACO-associated
@article{Zeininger2021,
title = {Single-Particle Catalysis: Revealing Intraparticle Pacemakers in Catalytic H2 Oxidation on Rh},
author = {Johannes Zeininger and Yuri Suchorski and Maximilian Raab and Sebastian Buhr and Henrik Grönbeck and Günther Rupprechter},
doi = {10.1021/acscatal.1c02384},
year = {2021},
date = {2021-07-27},
urldate = {2021-07-27},
journal = {ACS Catalysis},
volume = {11},
number = {15},
pages = {10020--10027},
publisher = {American Chemical Society (ACS)},
abstract = {Self-sustained oscillations in H_{2} oxidation on a Rh nanotip mimicking a single catalytic nanoparticle were studied by in situ field emission microscopy (FEM). The observed spatio-temporal oscillations result from the coupling of subsurface oxide formation/depletion with reaction front propagation. An original sophisticated method for tracking kinetic transition points allowed the identification of local pacemakers, initiating kinetic transitions and the nucleation of reaction fronts, with much higher temporal resolution than conventional processing of FEM video files provides. The pacemakers turned out to be specific surface atomic configurations at the border between strongly corrugated Rh{973} regions and adjacent relatively flat terraces. These structural ensembles are crucial for reactivity: while the corrugated region allows sufficient oxygen incorporation under the Rh surface, the flat terrace provides sufficient hydrogen supply required for the kinetic transition, highlighting the importance of interfacet communication. The experimental observations are complemented by mean-field microkinetic modeling. The insights into the initiation and propagation of kinetic transitions on a single catalytic nanoparticle demonstrate how in situ monitoring of an ongoing reaction on individual nanofacets can single out active configurations, especially when combined with atomically resolving the nanoparticle surface by field ion microscopy (FIM).},
keywords = {P08, TACO-associated},
pubstate = {published},
tppubtype = {article}
}