Topological Stone–Wales Defects Enhance Bonding and Electronic Coupling at the Graphene/Metal Interface

B. P. Klein, A. Ihle, S. R. Kachel, L. Ruppenthal, S. J. Hall, L. Sattler, S. M. Weber, J. Herritsch, A. Jaegermann, D. Ebeling, R. J. Maurer, G. Hilt, R. Tonner-Zech, A. Schirmeisen, J. M. Gottfried, ACS Nano 16, 11979-11987 (2022)

"Defects in Graphene subtly affect the structural and electronic properties. We perform a detailed joint experiment/theory investigation of molecular precursors of pristine graphene and Stone-Wales defects in graphene to assess the structural and spectroscopic changes imposed by defects."

Long-range dispersion-inclusive machine learning potentials for structure search and optimization of hybrid organic–inorganic interfaces

J. Westermayr, S. Chaudhuri, A. Jeindl, O. T. Hofmann, R. J. Maurer, Digital Discovery DOI:10.1039/D2DD00016D (2022)

"We present an ML approach that enables fast, yet accurate, structure optimizations by combining two different types of deep neural networks trained on high-level electronic structure data. The first model is a short-ranged interatomic ML potential trained on local energies and forces, while the second is an ML model of effective atomic volumes derived from atoms-in-molecules partitioning. The latter can be used to connect short-range potentials to well-established density-dependent long-range dispersion correction methods. For two systems, specifically gold nanoclusters on diamond (110) surfaces and organic π-conjugated molecules on silver (111) surfaces, we show the ability of the models to deliver highly efficient structure optimizations and semi-quantitative energy predictions of adsorption structures."

Dissipative tunneling rates through the incorporation of first-principles electronic friction in instanton rate theory. II. Benchmarks and applications

Y. Litman, E. S. Pos, C. L. Box, R. Martinazzo, R. J. Maurer, M. Rossi J. Chem. Phys. 156, 194107 (2022)

"Hydrogen chemistry at surfaces can involve nonadiabatic effects (NAEs) and quantum nuclear effects (NQEs). The theoretical modeling of such reactions presents a formidable challenge for theory. In this work, we derive a theoretical framework that captures both NQEs and NAEs and, due to its high efficiency, can be applied to first-principles calculations of reaction rates in high-dimensional realistic systems. More specifically, we develop a method that we coin ring polymer instanton with explicit friction, starting from the ring polymer instanton formalism applied to a system–bath model. In this second part, we present benchmark calculations and applications."

Dissipative tunneling rates through the incorporation of first-principles electronic friction in instanton rate theory. I. Theory

Y. Litman, E. S. Pos, C. L. Box, R. Martinazzo, R. J. Maurer, M. Rossi J. Chem. Phys. 156, 194106 (2022)

"Hydrogen chemistry at surfaces can involve nonadiabatic effects (NAEs) and quantum nuclear effects (NQEs). The theoretical modeling of such reactions presents a formidable challenge for theory. In this work, we derive a theoretical framework that captures both NQEs and NAEs and, due to its high efficiency, can be applied to first-principles calculations of reaction rates in high-dimensional realistic systems. More specifically, we develop a method that we coin ring polymer instanton with explicit friction, starting from the ring polymer instanton formalism applied to a system–bath model. In this first part, we describe the theory and derivation of this approach."

Direct Experimental Evidence for Substrate Adatom Incorporation into a Molecular Overlayer

P. J. Mouslez, L. A. Rochford, P. T. P. Ryan, P. Blowey, J. Lawrence, D. A. Duncan, H. Hussain, B. Sohail, T.-L. Lee, G. R. Bell, G. Costantini, R. J. Maurer, C. Nicklin, D. P. Woodruff, J. Phys. Chem. C 126, 7346 - 7355 (2022)

"We present the results of a detailed structural study of the Au(111)-F₄TCNQ system, combining surface characterization by STM, low-energy electron diffraction, and soft X-ray photoelectron spectroscopy with quantitative experimental structural information from normal incidence X-ray standing wave (NIXSW) and SXRD, together with dispersion-corrected density functional theory (DFT) calculations. SXRD measurements provide unequivocal evidence for the presence and location of Au adatoms, while the DFT calculations show this reconstruction to be strongly energetically favored"

Design Principles for Metastable Standing Molecules

H. H. Arefi, D.Corken, F. S.Tautz, R. J. Maurer, C. Wagner, J. Phys. Chem. C 126, 6880-6891 (2022)

"Here, we use density functional theory to study 3,4,9,10-perylene-tetracarboxylic dianhydride (PTCDA) standing on the Ag(111) surface as well as on the tip of a scanning probe microscope. We cast our results into a simple set of design principles for such metastable structures, the validity of which we subsequently demonstrate in two computational case studies. Our work proves the capabilities of computational nanostructure design in the field of metastable molecular structures and offers the intuition needed to fabricate new devices without tedious trial and error."

Thermodynamic Driving Forces for Substrate Atom Extraction by Adsorption of Strong Electron Acceptor Molecules

P. Ryan, P. J. Blowey, B. S. Sohail, L. A. Rochford, D. A. Duncan, T.-L. Lee, P. Starrs, G. Costantini, R. J. Maurer, J. Phys. Chem. C 126, 6082-6090 (2022)

"A quantitative structural investigation is reported, aimed at resolving the issue of whether substrate adatoms are incorporated into the monolayers formed by strong molecular electron acceptors deposited onto metallic electrodes. A combination of X-ray standing waves, STM, and DFT show that there is an energetic driving force for adatom incorporation into adsorbate structures of the strong acceptor F₄TCNQ on Ag(100) but not for the weaker acceptor TCNQ."

Adiabatic versus non-adiabatic electron transfer at 2D electrode materials

Dan-Qing Liu, Minkyung Kang, David Perry, Chang-Hui Chen, Geoff West, Xue Xia, Shayantan Chaudhuri, Zachary P. L. Laker, Neil R. Wilson, Gabriel N. Meloni, Marko M. Melander, Reinhard J. Maurer, Patrick R. Unwin, Nature Communications 12, 7110 (2021)

"Using scanning electrochemical cell microscopy, and co-located structural microscopy, the classical hexaamineruthenium (III/II) couple is measured on a graphene-metal electrode. Using model Hamiltonian and constant potential density functional theory, we can rationalize the fact that monolayer graphene shows faster kinetics than bilayer graphene and we are able to identify the electron transfer as dominantly adiabatic."

Nature Portfolio Blogpost

The stabilization potential of a standing molecule

Marvin Knol, Hadi H. Arefi, Daniel Corken, James Gardner, F. Stefan Tautz, Reinhard J. Maurer, and Christian Wagner, Science Advances 7, eabj9751 (2021)

"Here, we combine scanning probe experiments with ab initio potential energy calculations to investigate the thermal stability of a prototypical standing molecule. We reveal its generic stabilization mechanism, a fine balance between covalent and van der Waals interactions including the latter's long-range screening by many-body effects, and find a remarkable agreement between measured and calculated stabilizing potentials."

Warwick University Press Release

First-principles calculations of hybrid inorganic-organic interfaces: From state-of-the-art to best practice

Oliver T. Hofmann, Egbert Zojer, Lukas Hörmann, Andreas Jeindl, and R. J. Maurer, Phys. Chem. Chem. Phys. 23, 8132-8180 (2021)

"In this review, we discuss how to choose appropriate atomistic representations for the simulation of hybrid inorganic-organic interfaces. We provide tips and tricks on how to efficiently converge the self-consistent field cycle and to obtain accurate geometries. We particularly focus on potentially unexpected pitfalls and the errors they incur. As a summary, we provide a list of best practice rules for interface simulations that should especially serve as a useful starting point for less experienced users and newcomers to the field."

The Nuts and Bolts of Ab-Initio Core-Hole Simulations for K-shell X-Ray Photoemission and Absorption Spectra

B. Klein, S. J. Hall, R. J. Maurer, J. Phys. Condens. Matter 33, 154005 (2020)

"We present the numerical and technical details of our variants of the DeltaSCF and transition potential method (coined DeltaIP-TP) to simulate XPS and NEXAFS transitions. Using exemplary molecules in gas-phase, in bulk crystals, and at metal-organic interfaces, we systematically assess how practical simulation choices affect the stability and accuracy of simulations. We particularly focus on the choice of aperiodic or periodic description of systems and how spurious charge effects in periodic calculations affect the simulation outcomes. For the benefit of practitioners in the field, we discuss sensible default choices, limitations of the methods, and future prospects."

Determining the effect of hot electron dissipation on molecular scattering experiments at metal surfaces

C. L. Box, Y. Zhang, R. Yin, B. Jiang, R. J. Maurer, JACS Au 1, 164-173 (2020)

"Vibrational state-to-state scattering of NO on Au(111) provides a testing ground for developing various nonadiabatic theories, including electronic friction theory. This system is often cited as the prime example for the breakdown of electronic friction theory, a very efficient model accounting for dissipative forces on metal-adsorbed molecules due to the creation of electron-hole-pair excitations in the metal. Here we present a comprehensive quantitative analysis of the performance of molecular dynamics with electronic friction (MDEF) in describing vibrational state-to-state scattering of NO on Au(111) and connect directly to fundamental approximations. Our analysis provides a firm baseline for the future development of nonadiabatic dynamics methods to tackle problems in surface chemistry and photocatalysis."

Alkali Doping Leads to Charge-Transfer Salt Formation in a Two-Dimensional Metal-Organic Framework

P. J. Blowey, B. Sohail, L. A. Rochford, T. Lafosse, D. A. Duncan, P. T. P. Ryan, D. A. Warr, T.-L. Lee, G. Costantini, R. J. Maurer, and D. P. Woodruff, ACS Nano 14, 7475-7483 (2020)

"We show that the insertion of alkali atoms can significantly change the structure and electronic properties of a metal-organic interface. Coadsorption of tetracyanoquinodimethane (TCNQ) and potassium on a Ag(111) surface leads to the formation of a two-dimensional charge transfer salt, with properties quite different to those of the two-dimensional Ag adatom TCNQ metal-organic framework formed in the absence of K doping. We establish a highly accurate structural model by combination of quantitative XSW, STM, and DFT calculations. Full agreement between the experimental data and the computational prediction of the structure is only achieved by inclusion of a charge-transfer-scaled dispersion correction in the DFT, which correctly accounts for the effects of strong charge transfer on the atomic polarizability of potassium. "

Enhanced Bonding of Pentagon–Heptagon Defects in Graphene to Metal Surfaces: Insights from the Adsorption of Azulene and Naphthalene to Pt(111)

Benedikt P. Klein, S. Elizabeth Harman, Lukas Ruppenthal, Griffin M. Ruehl, Samuel J. Hall, Spencer J. Carey, Jan Herritsch, Martin Schmid, Reinhard J. Maurer, Ralf Tonner, Charles T. Campbell, and J. Michael Gottfried, Chem. Mater. 32, 1041-1053 (2020)

"We show here that the interface properties may be controlled by topological defects, such as the pentagon–heptagon (5–7) pairs, because of their strongly enhanced bonding to the metal. To measure the bond energy and other key properties not accessible for the embedded defects, we use azulene as a molecular model for the 5–7 defect. Comparison to its isomer naphthalene, which represents the regular graphene structure, reveals that azulene interacts more strongly with a Pt(111) surface. Using a combination of single-crystal adsorption calorimetry, x-ray photoelectron and photoabsorption spectroscopies (XPS/NEXAFS), and Density Functional Theory, we fully characterize the adsorption strength, the surface structure and surface chemistry of 5-7 defect systems on Pt(111). Our model study shows that the topology of the π-electron system strongly affects its bonding to a transition metal and thus can be utilized to tailor interface properties."

A symmetry adapted high dimensional neural network representation of electronic friction tensor of adsorbates on metals

Yaolong Zhang, Reinhard J. Maurer, Bin Jiang, J. Chem. Phys., just accepted (2019)

"In this work, we develop a new symmetry-adapted neural network representation of electronic friction, based on our recently proposed embedded atom neural network (EANN) framework. Unlike previous methods, our new approach can readily include both molecular and surface degrees of freedom, regardless of the type of surface. Tests on the H2+Ag(111) system show that this approach yields an accurate, efficient, and continuous representation of electronic friction, making it possible to perform large scale TDPT-based MDEF simulations to study both adiabatic and nonadiabatic energy dissipation in a unified framework."

Molecule–Metal Bond of Alternant versus Nonalternant Aromatic Systems on Coinage Metal Surfaces: Naphthalene versus Azulene on Ag(111) and Cu(111)

Benedikt P. Klein, Juliana M. Morbec, Markus Franke, Katharina K. Greulich, Malte Sachs, Shayan Parhizkar, Francois C. Boquet, Martin Schmidt, Samuel J. Hall, Reinhard J. Maurer, Bernd Meyer, Ralf Tonner, Christian Kumpf, Peter Kratzer, and J. Michael Gottfried, J. Phys. Chem. C just accepted, DOI: 10.1021/acs.jpcc.9b08824 (2019)

"The coverage-dependent interaction of Azulene and Naphthalene with Ag(111) and Cu(111) surfaces was studied with the normal-incidence X-ray standing wave (NIXSW) technique, near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, UV and X-ray photoelectron spectroscopies (UPS and XPS), and density functional theory (DFT). We analyse the interaction strength and charge-transfer at the molecule-metal interface by comparing simulated and measured NEXAFS spectra."

Computational design of metal-supported molecular switches: Transient ion formation during light- and electron-induced isomerisation of azobenzene

R. J. Maurer and K. Reuter, J. Phys. Condens Matter, DOI:10.1088/1361-648X/aaf0e1 (2018), Invited Article

"Using DFT and linear expansion Delta-Self-Consistent DFT excited-state calculations, we systematically analyse important design parameters that define successful light-induced molecular switching of azobenzene."

Interpretation of X-ray Absorption Spectroscopy in the Presence of Surface Hybridisation

Katharina Diller, Reinhard J. Maurer, Moritz Müller, Karsten Reuter, J. Chem. Phys. 146, 214701 (2017)

Accurate ab-initio core-level spectroscopy simulations of surface-adsorbed molecules reveal the details of surface hybridization.

Ab-initio tensorial electronic friction for molecules on metal surfaces: nonadiabatic vibrational relaxation

Reinhard J. Maurer, Mikhail Askerka, Victor S. Batista, John C. Tully, Phys. Rev. B. 94, 115432 (2016)

We present our efficient and robust ab-initio implementation of tensorial electronic friction and apply it to calculate vibrational lifetimes.

Global structure search for molecules on surfaces: Efficient sampling with curvilinear coordinates

Konstantin Krautgasser, Chiara Panosetti, Dennis Palagin, Karsten Reuter, Reinhard J. Maurer, J. Chem. Phys. 145, 084117 (2016)

We extend our curvilinear coordinate global optimization method to efficiently sample adsorbate structures on surfaces.

Switching of an Azobenzene-Tripod Molecule on Ag(111)

Katharina Scheil, Thiruvancheril G. Gopakumar, Julia Bahrenburg, Friedrich Temps, Reinhard J. Maurer, Karsten Reuter, Richard Berndt, J. Phys. Chem. Lett. 7, 2080-2084 (2016)

We observe and interpret the mechanism of multistate switching of an Azobenzene Tripod on Ag(111) using STM, STS and Density Functional Theory.

Adsorption structures and energetics of molecules on metal surfaces: Bridging experiment and theory

Reinhard J. Maurer, Victor G. Ruiz, Javier Camarillo-Cisneros, Wei Liu, Nicola Ferri, Karsten Reuter, Alexandre Tkatchenko, Prog. Surf. Sci. 91, 72-100 (2016)

By reviewing experiment and calculation data for structures and energies, we compose a benchmark database for molecules on metal surfaces.

Role of Tensorial Electronic Friction in Energy Transfer at Metal Surfaces

Mikhail Askerka, Reinhard J. Maurer, Victor S. Batista, John C. Tully, Phys. Rev. Lett. 116, 217601 (2016)
Editor’s Suggestion

We use time-dependent perturbation theory to calculate the full electronic friction tensor and study its relevance in the simulation of dynamics at surfaces.

Thermal and electronic fluctuations of flexible adsorbed molecules: Azobenzene on Ag(111)

Reinhard J. Maurer, Wei Liu, Igor Poltavsky, Thomas Stecher, Harald Oberhofer, Karsten Reuter, Alexandre Tkatchenko, Phys. Rev. Lett., 116, 146101 (2016)

Ab Initio molecular dynamics simulation of the free energy of desorption reveals collective electronic and thermal fluctuations that define the finite-temperature energetics of complex adsorbates.

Spin manipulation by creation of single-molecule radical cations

S. Karan, N. Li, Y. Zhang, Y. He, I-P. Hong, H. Song, J.-T. Lü, Y. Wang, L. Peng, K. Wu, G. S. Michelitsch, R. J. Maurer, K. Diller, K. Reuter, A. Weissmann, and R. Berndt, Phys. Rev. Lett., 116, 027201 (2016)

We investigate magnetic switching of all-trans-retinoic acid adsorbed on a Au(111) surface using Scanning Tunneling Microscopy and Density Functional Theory.

Interfacial charge rearrangement and intermolecular interactions: Density-functional theory study of free-base porphine adsorbed on Ag(111) and Cu(111)

M. Müller, K. Diller, R. J. Maurer, K. Reuter, J. Chem. Phys., 144, 024701 (2016)

We study the interactions and the self-assembly behaviour of Porphine on Ag(111) and Cu(111). We find significant substrate-mediated, and negligible direct lateral interactions.

Coverage-Driven Dissociation of Azobenzene on Cu(111): A Route Towards Defined Surface Functionalization

M. Willenbockel, R. J. Maurer, C. Bronner, M. Schulze, B. Stadtmüller, S. Soubatch, P. Tegeder, K. Reuter, F. S. Tautz, Chem. Commun., 51, 15324-15327 (2015)

Using X-ray Photoelectron Spectroscopy, X-ray Standing Waves and Density Functional Theory we discover a novel route towards surface functionalization by coverage-driven dissociation of Azobenzene on Cu(111)

Many Body Dispersion Effects in the Binding of Adsorbates on Metal Surfaces

R. J. Maurer, V. Ruiz, A. Tkatchenko, J. Chem. Phys., 143, 102808 (2015)

We study the effect of many body dispersion on the geometry and energetics of atoms, molecules and nanostructures adsorbed to a metal surface and find a ubiquitous importance of many body effects to correctly describe adsorbates.

Temperature-dependent templated growth of porphine thin films on the (111) facets of copper and silver

K. Diller, F. Klappenberger, F. Allegretti, A. C. Papagergiou, S. Fischer, D. A. Duncan, R. J. Maurer, J. A. Lloyd, S. Cheol Oh, K. Reuter, J. V. Barth, J. Chem. Phys. 141, 144703 (2014)

Using X-ray photoelectron spectroscopy, NEXAFS and Density Functional Theory we show the coverage dependent adlayer structure of porphine films

X-ray standing wave simulations based on Fourier vector analysis as a method to retrieve complex molecular adsorption geometries

G. Mercurio, R. J. Maurer, S. Hagen, F. Leyssner, J. Meyer, P. Tegeder, S. Soubatch, K. Reuter, F. S. Tautz, Front. Phys 2, 2 (2014)

An analysis method of x-ray standing wave data that enables the detailed adsorption geometry of large, complex adsorbates to be retrieved