Diffusion Rates for Hydrogen on Pd(111) from Molecular Quantum Dynamics Calculations

Abstract

Diffusion rates are calculated on the basis of van Hove's formula for the dynamical structure factor (DSF) related to particle scattering at mobile adsorbates. The formula is evaluated quantum mechanically using eigenfunctions obtained from three dimensional realistic models for H/Pd(111) derived from first principle calculations. Results are compatible with experimental data for H/Ru(0001) and H/Pt(111), if one assumes that the total rate obtained from the DSF is the sum of a diffusion and a friction rate. A simple kinetic model to support this assumption is presented.

Improved on-the-Fly MCTDH Simulations with Many-Body-Potential Tensor Decomposition and Projection Diabatization

“…(11) and to evaluate Eq. (14). To illustrate the effect of this algorithm update, we investigate the dynamics of proton transfer in salicylaldimine, as studied in our previous work.…”

“…[1][2][3][4][5][6] In MCTDH, the time-dependent Schrödinger equation (TDSE) is solved by introducing a wavefunction ansatz comprising a sum of Hartree products of single-particle functions (SPFs), along with their complex expansion coefficients; using the Dirac-Frenkel time-dependent variational principle, [7][8][9] one can then derive equations-of-motion for both the expansion coefficients and the SPFs, leading to an efficient method for propagating wavepackets which can, in principle, be converged to the exact quantum-mechanical result. The range of systems modelled to date with MCTDH is continually growing, spanning non-adiabatic dynamics in organic molecules, 2,10,11 transport on model surfaces, [12][13][14] and organometallic complexes. 15,16 In practice, two important general factors have constrained the application domain of MCTDH simulations.…”

Atom Tunneling in Chemistry

“…[229,230] Even though this Review mainly focuses on molecular systems,w ew ill now briefly discuss atom tunneling on surfaces.H ydrogen atoms have been frequently observed to tunnel in surface processes. [231][232][233] It was shown that the motion of hydrogen on Cu(001), [234][235][236][237] Pd/Cu (111), [238,239] Ru(0001), [240] W(110), [241] and Ni(100) [242][243][244] surfaces is enhanced by tunneling at low temperatures.E ven the motion of CO on aC u(111) surface was shown by scanning tunneling microscopy (STM) to occur below 6K,w ith atemperature-independent hopping rate. [245] In the field of heterogeneous catalysis,t he CO oxidation and the dissociative H 2 Od esorption as well as the OH dissociation on various metal (111) surfaces were shown to be affected by tunneling.…”

Der Tunneleffekt von Atomen in der Chemie

“…Auch wenn sich dieser Aufsatz hauptsächlich mit molekularen Systemen beschäftigt, behandeln wir hier kurz den Einfluss des Tunneleffekts auf Oberflächenprozesse . So wurde gezeigt, dass die Bewegung von Wasserstoff auf Cu(001)‐, Pd/Cu(111)‐, Ru(0001)‐, W(110)‐ und Ni(100)‐Oberflächen durch Tunneln bei niedrigen Temperaturen deutlich erleichtert ist. Durch Rastertunnelmikroskopie konnte gezeigt werden, dass sogar die Bewegung von CO bei tiefsten Temperaturen auf einer Cu(111)‐Oberfläche durch Atomtunneln ermöglicht wird und unterhalb von 6 K temperaturunabhängig ist …”