TY - JOUR A1 - Loncaric, Ivor A1 - Fuchsel, Gernot A1 - Juaristi, J. I. A1 - Saalfrank, Peter T1 - Strong Anisotropic Interaction Controls Unusual Sticking and Scattering of CO at Ru(0001) JF - Physical review letters N2 - Complete sticking at low incidence energies and broad angular scattering distributions at higher energies are often observed in molecular beam experiments on gas-surface systems which feature a deep chemisorption well and lack early reaction barriers. Although CO binds strongly on Ru(0001), scattering is characterized by rather narrow angular distributions and sticking is incomplete even at low incidence energies. We perform molecular dynamics simulations, accounting for phononic (and electronic) energy loss channels, on a potential energy surface based on first-principles electronic structure calculations that reproduce the molecular beam experiments. We demonstrate that the mentioned unusual behavior is a consequence of a very strong rotational anisotropy in the molecule-surface interaction potential. Beyond the interpretation of scattering phenomena, we also discuss implications of our results for the recently proposed role of a precursor state for the desorption and scattering of CO from ruthenium. Y1 - 2017 U6 - https://doi.org/10.1103/PhysRevLett.119.146101 SN - 0031-9007 SN - 1079-7114 VL - 119 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Loncaric, Ivor A1 - Alducin, Maite A1 - Saalfrank, Peter A1 - Juaristi, J. I. T1 - Femtosecond-laser-driven molecular dynamics on surfaces: Photodesorption of molecular oxygen from Ag(110) JF - Physical review : B, Condensed matter and materials physics N2 - We simulate the femtosecond-laser-induced desorption dynamics of a diatomic molecule from a metal surface by including the effect of the electron and phonon excitations created by the laser pulse. Following previous models, the laser-induced surface excitation is treated through the two temperature model, while the multidimensional dynamics of the molecule is described by a classical Langevin equation, in which the friction and random forces account for the action of the heated electrons. In this work we propose the additional use of the generalized Langevin oscillator model to also include the effect of the energy exchange between the molecule and the heated surface lattice in the desorption dynamics. The model is applied to study the laser-induced desorption of O-2 from the Ag(110) surface, making use of a six-dimensional potential energy surface calculated within density functional theory. Our results reveal the importance of the phonon mediated process and show that, depending on the value of the electronic density in the surroundings of the molecule adsorption site, its inclusion can significantly enhance or reduce the desorption probabilities. Y1 - 2016 U6 - https://doi.org/10.1103/PhysRevB.93.014301 SN - 1098-0121 SN - 1550-235X VL - 93 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Scholz, Robert A1 - Floss, Gereon A1 - Saalfrank, Peter A1 - Füchsel, Gernot A1 - Loncaric, Ivor A1 - Juaristi, J. I. T1 - Femtosecond-laser induced dynamics of CO on Ru(0001): Deep insights from a hot-electron friction model including surface motion JF - Physical review : B, Condensed matter and materials physics N2 - A Langevin model accounting for all six molecular degrees of freedom is applied to femtosecond-laser induced, hot-electron driven dynamics of Ru(0001)(2 x 2): CO. In our molecular dynamics with electronic friction approach, a recently developed potential energy surface based on gradient-corrected density functional theory accounting for van der Waals interactions is adopted. Electronic friction due to the coupling of molecular degrees of freedom to electron-hole pairs in the metal are included via a local density friction approximation, and surface phonons by a generalized Langevin oscillator model. The action of ultrashort laser pulses enters through a substrate-mediated, hot-electron mechanism via a time-dependent electronic temperature (derived from a two-temperature model), causing random forces acting on the molecule. The model is applied to laser induced lateral diffusion of CO on the surface, "hot adsorbate" formation, and laser induced desorption. Reaction probabilities are strongly enhanced compared to purely thermal processes, both for diffusion and desorption. Reaction yields depend in a characteristic (nonlinear) fashion on the applied laser fluence, as well as branching ratios for various reaction channels. Computed two-pulse correlation traces for desorption and other indicators suggest that aside from electron-hole pairs, phonons play a non-negligible role for laser induced dynamics in this system, acting on a surprisingly short time scale. Our simulations on precomputed potentials allow for good statistics and the treatment of long-time dynamics (300 ps), giving insight into this system which hitherto has not been reached. We find generally good agreement with experimental data where available and make predictions in addition. A recently proposed laser induced population of physisorbed precursor states could not be observed with the present low-coverage model. Y1 - 2016 U6 - https://doi.org/10.1103/PhysRevB.94.165447 SN - 2469-9950 SN - 2469-9969 VL - 94 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Saalfrank, Peter A1 - Juaristi, J. I. A1 - Alducin, Maite A1 - Blanco-Rey, Maria A1 - Muino, R. Diez T1 - Vibrational lifetimes of hydrogen on lead films : an ab initio molecular dynamics with electronic friction (AIMDEF) study JF - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr N2 - Using density functional theory and Ab Initio Molecular Dynamics with Electronic Friction (AIMDEF), we study the adsorption and dissipative vibrational dynamics of hydrogen atoms chemisorbed on free-standing lead films of increasing thickness. Lead films are known for their oscillatory behaviour of certain properties with increasing thickness, e.g., energy and electron spill-out change in discontinuous manner, due to quantum size effects [G. Materzanini, P. Saalfrank, and P.J.D. Lindan, Phys. Rev. B 63, 235405 (2001)]. Here, we demonstrate that oscillatory features arise also for hydrogen when chemisorbed on lead films. Besides stationary properties of the adsorbate, we concentrate on finite vibrational lifetimes of H-surface vibrations. As shown by AIMDEF, the damping via vibration-electron hole pair coupling dominates clearly over the vibration-phonon channel, in particular for high-frequency modes. Vibrational relaxation times are a characteristic function of layer thickness due to the oscillating behaviour of the embedding surface electronic density. Implications derived from AIMDEF for frictional many-atom dynamics, and physisorbed species will also be given. (C) 2014 AIP Publishing LLC. Y1 - 2014 U6 - https://doi.org/10.1063/1.4903309 SN - 0021-9606 SN - 1089-7690 VL - 141 IS - 23 PB - American Institute of Physics CY - Melville ER -