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."

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."

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."

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. "

DFTB+, a software package for efficient approximate density functional theory based atomistic simulations

B. Hourahine, B. Aradi et al., J. Chem. Phys. 152, 124101 (2020)

"DFTB+ is a versatile community developed open source software package offering fast and efficient methods for carrying out atomistic quantum mechanical simulations. We give an overview of the recently developed capabilities of the DFTB+ code, demonstrating with a few use case examples, discuss the strengths and weaknesses of the various features, and also discuss on-going developments and possible future perspectives."

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."

Structure and Stability of Molecular Crystals with Many Body Dispersion Inclusive Density Functional Tight Binding

Majid Mortazavi, Jan Gerit Brandenburg, Reinhard J. Maurer, Alexandre Tkatchenko, J. Phys. Chem. Lett. 9, 399-405 (2018)

"We show the ability of many-body-dispersion-inclusive tight-binding methodology to accurately predict the structure of polymorphic organic molecular crystals."

Charge-Population Based Dispersion Interactions for Molecules and Materials

Martin Stöhr, Georg S. Michelitsch, John C. Tully, Karsten Reuter, Reinhard J. Maurer, J. Chem. Phys., 144, 151101 (2016)

A simple correlation between atomic polarizability and hybridization enables us to couple semi-empirical electronic structure methods with electron density-derived dispersion correction methods.

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.

Dynamics of Spatially Confined Bisphenol A Trimers in a Unimolecular Network on Ag(111)

Julian A. Lloyd, Anthoula C. Papageorgiou, Sybille Fischer, Seung Cheol Oh, Özge Saglam, Katharina Diller, David A. Duncan, Francesco Allegretti, Florian Klappenberger, Martin Stöhr, Reinhard J. Maurer, Karsten Reuter, Joachim Reichert, Johannes V. Barth, Nano Lett., 16, 1884-1889 (2016)

A combination of STM, XPS, NEXAFS experiments, Density Functional Theory and Density Functional Tight-Binding simulations reveals interesting thermally-induced confined dynamics of adsorbates.

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.