Publications

@article{Imre_2026a,

title = {An improved reliability factor for quantitative low-energy electron diffraction},

author = {Alexandra M. Imre and Lutz Hammer and Ulrike Diebold and Michele Riva and Michael Schmid},

doi = {10.1088/1361-648X/ae4af8},

year  = {2026},

date = {2026-02-26},

journal = {Journal of Physics: Condensed Matter},

abstract = {Quantitative low-energy electron diffraction [LEED I(V) or LEED I(E)], which evaluates the diffraction intensities I as a function of the electron energy, is a versatile technique for the study of surface structures. The technique is based on optimizing the agreement between experimental and calculated intensities. Today, the most commonly used measure of agreement is Pendry's R_{P}. While R_{P} has many advantages it also has severe shortcomings, as it is a noisy target function for optimization and very sensitive to small offsets of the intensity. Furthermore, R_{P} = 0, which is meant to imply perfect agreement between two I(E) curves, can also be achieved by qualitatively very different curves. We present a modified R_{S}, which can be used as a direct replacement for R_{P}, but avoids these shortcomings. We also demonstrate that R_{S} is as good as R_{P} or better in steering the optimization to the correct result in the case of imperfections in the experimental data, while another common R factor, R_{ZJ} (suggested by Zanazzi and Jona) is worse in this respect.},

keywords = {P02},

pubstate = {published},

tppubtype = {article}

}

@article{Wang_2026a,

title = {Hydrogen Activation via Dihydride Formation on a Rh_{1}/Fe_{3}O_{4}(001) Single-Atom Catalyst},

author = {Chunlei Wang and Panukorn Sombut and Lena Puntscher and Nail Barama and Maosheng Hao and Florian Kraushofer and Jiri Pavelec and Matthias Meier and Florian Libisch and Michael Schmid and Ulrike Diebold and Cesare Franchini and Gareth S. Parkinson},

doi = {10.1002/anie.202525745},

year  = {2026},

date = {2026-02-18},

urldate = {2026-02-18},

journal = {Angewandte Chemie International Edition},

pages = {e25745},

abstract = {Hydrogen activation is a key elementary step in catalytic hydrogenation. In heterogeneous catalysis, it usually proceeds through dissociative adsorption on metal nanoparticles followed by surface diffusion or spillover, whereas homogeneous catalysts activate H_{2} through dihydride or dihydrogen intermediates at a single metal center. Here, we show that isolated Rh adatoms supported on Fe_{3}O_{4}(001) activate hydrogen through formation of a stable dihydride species without atomic H spillover. Temperature-programmed desorption, x-ray photoelectron spectroscopy, and scanning tunneling microscopy collectively reveal strong (≈1 eV) hydrogen adsorption exclusively at isolated Rh_{1} sites, while isotope-exchange experiments further demonstrate that hydrogen remains localized. Density-functional theory-based calculations indicate a barrierless conversion from molecular H_{2} to the dihydride, and random-phase approximation calculations further confirm the relative stability of the dihydride. Together, these results show that single-atom Rh sites cleave hydrogen through a dihydride pathway analogous to homogeneous complexes, establishing a mechanistic bridge between homogeneous and heterogeneous catalysis.},

keywords = {P02, P04, P07},

pubstate = {published},

tppubtype = {article}

}

@article{Montero_2026a,

title = {Comparing the Mechanical and Thermodynamic Definitions of Pressure in Ice Nucleation},

author = {Pablo Montero de Hijes and K Shi and C Vega and Christoph Dellago},

doi = {10.1021/acs.jpclett.5c03700},

year  = {2026},

date = {2026-02-12},

journal = {The Journal of Physical Chemistry Letters},

abstract = {Crystal nucleation studies using hard-sphere and Lennard-Jones models have shown that the actual (mechanical) pressure within the nucleus is lower than that in the surrounding liquid. Here, we use the mechanical route to obtain the pressure for an ice nucleus in supercooled water (TIP4P/Ice) at 1 bar and 247 K. From this pressure, we obtain the interfacial stress using a thermodynamic definition consistent with mechanical arguments. Moreover, we compare the mechanical pressure with the thermodynamic pressure of bulk ice at an equal chemical potential and the interfacial stress with the interfacial free energy. Furthermore, we investigate these properties on the basal plane. We find that unlike in hard-sphere and Lennard-Jones systems, mechanical and thermodynamic pressures agree for the nucleus, and the interfacial stress and free energy are comparable. However, the basal interface displays an interfacial stress nearly twice its interfacial free energy, suggesting that this agreement may be dependent on the system, underscoring the limitations of mechanical routes to solid–liquid interfacial free energies.},

keywords = {P12},

pubstate = {published},

tppubtype = {article}

}

@article{Barlocco_2026a,

title = {Influence of nitrogen functional groups in carbon-based supports anchoring Pt nanoclusters and single atoms for efficient ammonia borane hydrolysis},

author = {Ilaria Barlocco and Silvio Bellomi and Bianca M. C. Anghinelli and Xiaowei Chen and Juan J. Delgado and Marta Stucchi and Laura Prati and Karin Föttinger and Alberto Villa},

doi = {10.1039/D5CC06925D},

year  = {2026},

date = {2026-02-05},

urldate = {2026-02-05},

journal = {Chemical Communications},

abstract = {A Pt(II) precursor was impregnated onto graphite (C) and carbon nitride (CN_{x}), successfully forming subnanometric Pt clusters and single atoms. The N species on CN_{x} modified the electronic and topological structure of the metal, improving the catalytic properties of the Pt/CN_{x} catalyst in evolving hydrogen from NH_{3}BH_{3}. This was rationalised by combining HR-TEM and XPS characterisation with DFT computational analysis.},

keywords = {P10},

pubstate = {published},

tppubtype = {article}

}

@article{CanoBlanco_2025a,

title = {Comparative study of multi-element modification and rhodium promotion of Co_{3}O_{4}-based spinel catalysts for N_{2}O decomposition},

author = {Daniel C. Cano-Blanco and Jarne van Aubel and Silvio Bellomi and Ivo Alxneit and Karin Föttinger and Oliver Kröcher and Davide Ferri},

doi = {10.1016/j.apcata.2025.120681},

year  = {2026},

date = {2026-01-25},

urldate = {2026-01-25},

journal = {Applied Catalysis A: General},

volume = {710},

pages = {120681},

abstract = {The removal of nitrous oxide (N_{2}O) from industrial flue gases remains a significant environmental challenge due to the intrinsic kinetic stability of the N_{2}O molecule. Among available abatement technologies, the direct catalytic decomposition of N_{2}O into harmless N_{2} and O_{2} (deN_{2}O) represents a promising, reagent-free solution. In this study, we systematically screened a series of catalysts obtained from Co_{3}O_{4} by addition of transition elements, magnesium and aluminum (10 wt%), and analog series with addition of rhodium (Rh; 1 wt%), from which Co-Al-Rh emerged as the most active catalyst formulation. Characterization by H_{2}-TPR and XPS indicated improvement in the redox performance and increasing weakening of the Co-O bond upon addition of a second element and of Rh. The addition of Rh resulted also in a significant enhancement in catalytic activity. Complementary kinetic studies revealed a shift in the rate-determining step (RDS) between N-O bond cleavage and O_{2} desorption, depending on catalyst composition. These results highlight the critical role of Co-O bond weakening in facilitating oxygen mobility and promoting activity.},

keywords = {P10},

pubstate = {published},

tppubtype = {article}

}

@article{Li_2025a,

title = {Probing the Structure of D_{2}O Ice Layers on ALD-grown ZrO_{2}, Al_{2}O_{3} and TiO_{2} Thin Films by Sum Frequency Generation (SFG) Spectroscopy},

author = {Xia Li and Susanne Gross and Thomas Haunold and Moon-Hyung Jang and Markéta Zukalová and Martin Jindra and Joanna Elzbieta Olszówka and Yu Lei and Stefan Vajda and Günther Rupprechter},

doi = {10.1039/D5FD00152H},

year  = {2025},

date = {2025-12-16},

journal = {Faraday Discussions},

abstract = {Sum frequency generation (SFG) spectroscopy was applied to investigate D_{2}O adsorption on atomic layer deposition (ALD)–grown Al_{2}O_{3}, ZrO_{2}, and TiO_{2} films at 94 ± 1 K. Film composition and thickness were characterized by ellipsometry and X-ray photoelectron spectroscopy (XPS). Additional SFG measurements were conducted on the SiO_{2}/Si wafer and on a CoO film prepared by oxidizing Co foil. At D_{2}O exposure below 3 000 L, the spectra were dominated by interfacial features originating from the ice-oxide interface. These spectra exhibited a weak, broad O–D stretching band (OD_{3}) centered at 2650 cm^{-1}, attributed to water molecules hydrogen-bonded to the oxide surface; this assignment was supported by the absence of the OD_{3} feature on the SiO_{2}/Si substrate. A sharp peak at 2730 cm^{-1} was also observed and assigned to the “free” O–D stretch (non-hydrogen-bonded with any neighboring molecule) of surface D_{2}O molecules pointing into the vapor phase. Upon increasing D_{2}O exposure, both the OD_{3} and “free” OD bands decreased in intensity and were replaced by weakly hydrogen-bonded OD_{2} and strongly hydrogen-bonded OD_{1} modes associated with the ice-vapor interface. As the exposure increased further, the OD_{2} and OD_{2} bands shifted to lower wavenumbers (2310 to 2284 cm^{-1}) and became stronger, with the OD_{1} mode exhibiting a larger red shift and more pronounced intensity enhancement. No significant differences in water structure were observed on the Al_{2}O_{3}, ZrO_{2}, and CoO films at the ice-vapor interfaces, apart from an approximately fivefold reduction in intensity on CoO, which is attributed to signal scattering from the rough CoO film/Co foil surface. However, when D_{2}O exposure reached ≥30 000 L, the OD_{1} band on the TiO_{2} surfaces decreased substantially in intensity and shifted to much lower wavenumbers (2065 cm^{-1} at 30 000 L; 2030 cm^{-1} at 102 000 L) than on Al_{2}O_{3} (2283 cm^{-1} at 90 000 L), ZrO_{2} (2293 cm^{-1} at 30 000 L), and CoO (2284 cm^{-1} at 900 000 L), indicating specific hydrogen-bonding interactions on the TiO_{2} surface.},

keywords = {P08},

pubstate = {published},

tppubtype = {article}

}

@article{Schmiedmayer_2025a,

title = {Equivariant machine learning of electric field gradients—Predicting the quadrupolar coupling constant in the MAPbI_{3} phase transition},

author = {Bernhard Schmiedmayer and Jop W. Wolffs and Gilles A. de Wijs and Arno P. M. Kentgens and Jonathan Lahnsteiner and Georg Kresse},

doi = {10.1063/5.0301056},

year  = {2025},

date = {2025-12-02},

journal = {The Journal of Chemical Physics},

volume = {163},

pages = {214110},

abstract = {We present a strategy combining machine learning and first-principle calculations to achieve highly accurate nuclear quadrupolar coupling constant predictions. Our approach employs two distinct machine-learning frameworks: a machine-learned force field to generate molecular dynamics trajectories and a second model for electric field gradients that preserves rotational and translational symmetries. By incorporating thermostat-driven molecular dynamics sampling, we enable the prediction of quadrupolar coupling constants in highly disordered materials at finite temperatures. We validate our method by predicting the tetragonal-to-cubic phase transition temperature of the organic–inorganic halide perovskite MAPbI_{3}, obtaining results that closely match experimental data.},

keywords = {P03},

pubstate = {published},

tppubtype = {article}

}

@article{Wadhwa_2025a,

title = {Machine learning study of surface reconstructions of the Cu_{2}⁢O⁡(111) surface},

author = {Payal Wadhwa and Michael Schmid and Georg Kresse},

doi = {10.1103/sfjm-1gyr},

year  = {2025},

date = {2025-11-17},

journal = {Physical Review B},

volume = {112},

issue = {20},

pages = {205420},

abstract = {The atomic structure of the most stable reconstructed surface of cuprous oxide (Cu_{2}⁢O)⁢(111) surface has been a longstanding topic of debate. In this study, we develop on-the-fly machine-learned force fields (MLFFs) to systematically investigate the various reconstructions of the Cu_{2}⁢O⁡(111) surface under stoichiometric as well as O- and Cu-deficient or rich conditions, focusing on both (√3×√3⁢)R⁢30∘ and (2×2) supercells. By utilizing parallel tempering simulations supported by MLFFs, we confirm that the previously described nanopyramidal and Cu-deficient (1×1) structures are the lowest energy structures from moderately to strongly oxidizing conditions. In addition, we identify two promising nanopyramidal reconstructions at highly reducing conditions, a stoichiometric one and a Cu-rich one. Surface energy calculations performed using spin-polarized PBE, PBE+𝑈, r2⁢SCAN, and HSE06 functionals show that the previously known Cu-deficient configuration and nanopyramidal configurations are at the convex hull (and, thus, equilibrium structures) for all functionals, whereas the stability of the other structures depends on the functional and is therefore uncertain. Our findings demonstrate that on-the-fly trained MLFFs provide a simple, efficient, and rapid approach to explore the complex surface reconstructions commonly encountered in experimental studies, and also enhance our understanding of the stability of Cu_{2}⁢O⁡(111) surfaces.},

keywords = {P02, P03},

pubstate = {published},

tppubtype = {article}

}

@article{Huetner_2025a,

title = {Surface reconstructions govern ice nucleation on silver iodide},

author = {Johanna I. Hütner and Andrea Conti and David Kugler and Franziska Sabath and Kim Noelle Dreier and Hans-Georg Stammler and Florian Mittendorfer and Angelika Kühnle and Michael Schmid and Ulrike Diebold and Jan Balajka},

doi = {10.1126/sciadv.aea2378},

year  = {2025},

date = {2025-10-31},

journal = {Science Advances},

volume = {11},

number = {44},

pages = {eaea2378},

abstract = {Silver iodide (AgI) is among the most effective ice-nucleating agents, attributed to its close lattice match with hexagonal ice. However, the atomic-level mechanism behind its efficiency remains unclear. The basal surfaces of AgI are polar and inherently unstable, necessitating a compensation mechanism, such as surface reconstruction, which may disrupt the favorable lattice match with ice. We combine noncontact atomic force microscopy with advanced computational modeling to determine the atomic structure of basal AgI surfaces in ultrahigh vacuum. The Ag-terminated (0001) surface exhibits a (2 × 2) reconstruction with ordered Ag vacancies, preserving a hexagonal arrangement of surface atoms that facilitates epitaxial ice growth. In contrast, the I-terminated (0001) surface adopts a complex rectangular reconstruction, incompatible with continuous ice layer formation. These findings highlight the decisive role of surface atomic structure and indicate that the Ag-terminated basal plane is primarily responsible for efficient ice nucleation on AgI.},

keywords = {P02, P04},

pubstate = {published},

tppubtype = {article}

}

@article{Eder_2025a,

title = {Multi-technique characterization of rhodium gem-dicarbonyls on TiO_{2}(110)},

author = {Moritz Eder and Faith J. Lewis and Johanna I. Hütner and Panukorn Sombut and Maosheng Hao and David Rath and Paul Ryan and Jan Balajka and Margareta Wagner and Matthias Meier and Cesare Franchini and Gianfranco Pacchioni and Ulrike Diebold and Michael Schmid and Florian Libisch and Jiři Pavelec and Gareth S. Parkinson},

doi = {10.1039/D5SC04889C},

year  = {2025},

date = {2025-10-16},

journal = {Chemical Science},

abstract = {Gem-dicarbonyls of transition metals supported on metal (oxide) surfaces are common intermediates in heterogeneous catalysis. While infrared (IR) spectroscopy is a standard tool for detecting these species on powder catalysts, the ill-defined crystallographic environment renders data interpretation challenging. In this work, we apply a multi-technique surface science approach to investigate rhodium gem-dicarbonyls on a single-crystalline rutile TiO_{2}(110) surface. We combine spectroscopy, scanning probe microscopy, and density functional theory (DFT) to determine their location and coordination on the surface. IR spectroscopy shows the successful creation of gem-dicarbonyls on a titania single crystal by exposing deposited Rh atoms to CO gas, followed by annealing to 200–250 K. Low-temperature scanning tunneling microscopy (STM) and non-contact atomic force microscopy (nc-AFM) data reveal that these complexes are mostly aligned along the [001] crystallographic direction, corroborating theoretical predictions. Notably, X-ray photoelectron spectroscopy (XPS) data reveal multiple rhodium species on the surface, even when the IR spectra show only the signature of rhodium gem-dicarbonyls. As such, our results highlight the complex behavior of carbonyls on metal oxide surfaces, and demonstrate the necessity of multi-technique approaches for the adequate characterization of single-atom catalysts.},

keywords = {P02, P04, P07},

pubstate = {published},

tppubtype = {article}

}