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."

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."

Effect of electron donating/withdrawing groups on molecular photoswitching of functionalized hemithioindigo derivatives: a computational multireference study

M. Lea, V. Stavros, R. J. Maurer, ChemPhotoChem, DOI: 10.1002/cptc.202100290 (2022)

"The mechanism of photoswitching for hemithioindigo cannot be described by pure dihedral rotation around the central carbon-carbon bond. A complementary motion, often pyramidalization, is required to facilitate radiationless internal conversion. This computational study, explores how the inclusion of electron-withdrawing and electron-donating substituents alters the excited state potential energy surfaces and the mechanism of photoisomerization. The predicted changes in energy landscapes reflect the acceleration or slowing of the photoisomerization process for different derivatives that is also observed in experiment."

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

Plasmonic enhancement of molecular hydrogen dissociation on metallic magnesium nanoclusters

Oscar Douglas-Gallardo, Connor L. Box, Reinhard J. Maurer, Nanoscale 13, 11058-11068 (2021)

"The optical and catalytic properties of magnesium nanoclusters are characterized in the context of plasmonic catalysis. Our Time-Dependent DFTB and DFT simulations show that plasmonic enhancement of hydrogen dissociation and evolution on magnesium nanoclusters is viable."

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. "

Tracking Metal Electrodeposition Dynamics from Nucleation and Growth of a Single Atom to Crystalline Nanoparticle

H. E. M. Hussein, R. J. Maurer, H. Amari, J. J. P. Peters, L. Meng, R. Beanland, M. E. Newton, J. V. Macpherson, ACS Nano 12, pp. 7388-7396 (2018)

"Identical Location Scanning Transmission Electron Microscopy and Density Functional Theory calculations give the first account of electrochemically-driven gold deposition with single-atom resolution."