Chiral and catalytic effects of site-specific molecular adsorption

Open access funded by Max Planck Society. The authors acknowledge the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany’s Excellence Strategy-EXC-2123 Quantum Frontiers - 390837967; Core program PC2-PN23080202 and the PN-III-P2-2.1-PED-2021-0378 (contract no. 575PED/2022) granted projects, financed by the Romanian Ministry of Research, Innovation and Digitalization/UEFISCDI; and the generous allocation of computer time at the computing center of Donostia International Physics Center and at the Red Española de Supercomputación (project QHS-2021-2-0019). A.A. acknowledges support from Project No. PID2019-103910GB-I00, funded by MCIN/AEI/10.13039/501100011033/ and FEDER Una manera de hacer Europa, and Project No. IT-1527-22 funded by the Basque Government.The changes of properties and preferential interactions based on subtle energetic differences are important characteristics of organic molecules, particularly for their functionalities in biological systems. Only slightly energetically favored interactions are important for the molecular adsorption and bonding to surfaces, which define their properties for further technological applications. Here, prochiral tetracenothiophene molecules are adsorbed on the Cu(111) surface. The chiral adsorption configurations are determined by Scanning Tunneling Microscopy studies and confirmed by first-principles calculations. Remarkably, the selection of the adsorption sites by chemically different moieties of the molecules is dictated by the arrangement of the atoms in the first and second surface layers. Furthermore, we have investigated the thermal effects on the direct desulfurization reaction that occurs under the catalytic activity of the Cu substrate. This reaction leads to a product that is covalently bound to the surface in chiral configurations.Publisher PDFPeer reviewe

Controlling single molecule conductance by a locally induced chemical reaction on individual thiophene units

The authors acknowledge the Emmy-Noether-Program of the Deutsche Forschungsgemeinschaft, the SFB 767, Core Program PN19-03 (contract number 21 N/08.02.2019) founded by the Romanian Ministry of Research and Innovation, Basque Departamento de Universidades e Investigación (grant no. IT-756-13), the Spanish Ministerio de Economía y Competitividad (grant no. FIS2013-48286-C2-8752-P and FIS2016-75862-P) andthe Operational Programme Research, Development and Education financed by European Structural and Investment Funds and the Czech Ministry of Education, Youth and Sports (Project No. SOLID21 CZ.02.1.01/0.0/0.0/16_019/0000760).Among the prerequisites for the progress of single‐molecule‐based electronic devices are a better understanding of the electronic properties at the individual molecular level and the development of methods to tune the charge transport through molecular junctions. Scanning tunneling microscopy (STM) is an ideal tool not only for the characterization, but also for the manipulation of single atoms and molecules on surfaces. The conductance through a single molecule can be measured by contacting the molecule with atomic precision and forming a molecular bridge between the metallic STM tip electrode and the metallic surface electrode. The parameters affecting the conductance are mainly related to their electronic structure and to the coupling to the metallic electrodes. Here, the experimental and theoretical analyses are focused on single tetracenothiophene molecules and demonstrate that an in situ‐induced direct desulfurization reaction of the thiophene moiety strongly improves the molecular anchoring by forming covalent bonds between molecular carbon and copper surface atoms. This bond formation leads to an increase of the conductance by about 50 % compared to the initial state.Publisher PDFPeer reviewe

Magnetic coupling between 3d transition metal adatoms on graphene supported by metallic substrates

The role of a metallic substrate in the interaction between 3d transition metal magnetic atoms adsorbed on graphene is explored for Ir(111), Cu(111) and Ni(111) surfaces. As a general rule, we find that exchange coupling between impurities is essentially determined by the graphene layer and it varies smoothly along the series of 3d atoms for Ir(111) and Cu(111) surfaces, except when resonances appear close to the Fermi level. This universal behavior is at the heart of our main conclusion: the weak interaction between graphene and the underlaying Ir and Cu metal surfaces does not alter appreciably the coupling between magnetic impurities. Therefore, we dare to speculate that previous results based on calculations with freestanding graphene are physically sound and correct. However, in the case of Ni(111) additional effects appear due to the metal surface magnetization.The authors thank the Basque Departamento de Universidades e Investigación (grant no. IT-756-13) and the Spanish Ministerio de Economía y Competitividad (grant numbers FIS2013-48286-C2-8752-P and FIS2016-75862-P) for financial support.Peer Reviewe

Isotope effects in Eley-Rideal and hot-atom abstraction dynamics of hydrogen from tungsten (100) and (110) surfaces

The influence of isotopic substitutions on the recombination dynamics of molecular hydrogen under normal incidence scattering of hydrogen isotopes on H(D,T)-precovered W(100) and W(110) surfaces is investigated. Quasiclassical trajectory simulations on density functional theory based potential energy surfaces are first performed within the single adsorbate limit, thus focusing on the Eley-Rideal abstraction. Significant isotope effects show up regardless of surface symmetry. Homonuclear recombinations (H-on-H, D-on-D, and T-on-T) lead to very similar cross sections, whereas for heteronuclear processes (H-on-D, D-on-H,...), cross sections are ordered by the mass ratio between the impinging atom and the adsorbate. The diatom energy partitioning is also affected by isotopic substitution. Similar effects, though less pronounced, appear for hot-atom abstraction on W(110) at θ = 0.25 ML surface coverage.The authors acknowledge the support of France Grilles for providing computing resources on the French National Grid Infrastructure and the Mesocentre de Calcul Intensif Aquitain (MCIA). R.P., C.C., and P.L. acknowledge ECOS-sud program for funding. MAN and RDM acknowledge financial support by the Gobierno Vasco - UPV/EHU (Grant No. IT756-13) and the Spanish Ministerio de Economia y Competitividad (Grant No. FIS2013-48286-C02-02-P).Peer Reviewe

Size Dependence of the Dissociation Process of Spherical Hydrate Particles via Microsecond Molecular Dynamics Simulations

The dissociation process of spherical sII mixed methane-propane hydrate particles in liquid hydrocarbon was investigated via microsecond-long Molecular Dynamics simulations. A strong dependence of the melting temperature on the particle size was found. Analysis in the context of the Gibbs-Thomson effect provided insights into the fundamental properties of gas hydrates.The authors thank Clariant for the financial support and to allow for the work to be published. We acknowledge PRACE for awarding us access to JUWELS at GCS@FZJ, Germany. The authors thankfully acknowledge the computer resources at Altamira and the technical support provided by the University of Cantabria(RES-QS-2021-1-0031).Peer ReviewedPostprint (author's final draft

Energy dissipation to tungsten surfaces upon Eley–Rideal recombination of N2 and H2

Quasiclassical molecular dynamics simulations are performed to investigate energy dissipation to the (100) and (110) tungsten surfaces upon Eley–Rideal (ER) recombination of H2 and N2. Calculations are carried out within the single adsorbate limit under normal incidence. A generalized Langevin surface oscillator (GLO) scheme is used to simulate the coupling to phonons, whereas electron–hole (e-h) pair excitations are implemented using the local density friction approximation (LDFA). Phonon excitations are found to reduce the ER reactivity for N2 recombination, but do not affect H abstraction. In contrast, the effect of e-h pair excitations on the ER recombination cross section is small for N2, but can be important for H2. The analysis of the energy lost by the recombined species shows that most of the energy is dissipated into phonon excitations in the N2 recombination and into electronic excitations in the H2 recombination. In all cases, the energy dissipated into e-h pairs is taken away from the translational kinetic energy of the formed molecules, whereas dissipation to phonons, only significant for N2, also affects vibration. Interestingly, the electron mediated energy losses are found to be smaller in the case of N2 when surface motion is allowed.O.G., J.I.J., and M.A. acknowledge financial support by the Basque Departamento de Educacion, Universidades e Investigacion, the University of the Basque Country UPV/EHU (Grant No IT-756-13) and the Spanish Ministerio de Economia y Competitividad (Grant No. FIS2013-48286-C2-2-P). O.G., M.A., and P.L. acknowledge the IDEX Bordeaux (ANR-10-IDEX-03-02) and Euskampus for fundings.Peer Reviewe

Hydrogen abstraction from metal surfaces: when electron–hole pair excitations strongly affect hot-atom recombination

Using molecular dynamics simulations, we predict that the inclusion of nonadiabatic electronic excitations influences the dynamics of preadsorbed hydrogen abstraction from the W(110) surface by hydrogen scattering. The hot-atom recombination, which involves hyperthermal diffusion of the impinging atom on the surface, is significantly affected by the dissipation of energy mediated by electron–hole pair excitations at low coverage and low incidence energy. This issue is of importance as this abstraction mechanism is thought to largely contribute to molecular hydrogen formation from metal surfaces.O. G., J. I. J, and M. A. acknowledge financial support by the Basque Departamento de Educación, Universidades e Investigación, the University of the Basque Country UPV/EHU (Grant No IT-756-13), and the Spanish Ministerio de Economía y Competitividad (Grant No. FIS2013-48286-C2-2-P). O. G., M. A., and P. L. acknowledge the IDEX Bordeaux (ANR-10-IDEX-03-02) and Euskampus for funding. Computational resources were provided by the DIPC computing center, the Mésocentre de Calcul Intensif Aquitain (MCIA).Peer reviewe

Phonon and electron excitations in abstraction processes from metallic surfaces

Resumen del trabajo presentado al CECAM workshop “Challenges in reaction dynamics of gas-surface interactions and methodological advances in dissipative and non-adiabatic processes”, celebrado en Albi (Francia) del 26 al 29 de junio de 2017.The rationalization of elementary processes at surfaces is of prime importance for numerous natural and technological areas. From a fundamental point of view, the way the energy concomitant to any chemical reaction is distributed among the desorbing molecules degrees-of-freedom and the surface is not entirely pictured. Over the last few years, we have been developing molecular dynamics simulations to investigate this issue for the recombination of H2 and N2 resulting from atomic adsorbate abstraction by atom scattering off the W(100) and W(110) covered surfaces. Potential energy surfaces, built from density functional (DFT) theory calculations, have been used to simulate, within the framework of classical dynamics (including semiclassical corrections), the subpicosecond Eley- Rideal and Hot-Atom processes. The implementation of effective models to account for energy dissipation to surface phonons and electron-hole pair excitations, have allowed to rationalize the nonadidabatic dynamics of atom abstraction at metal surfaces. Some examples of this ongoing research will be here shown.Peer reviewe