Femtosecond laser induced associative desorption of H2 from Ru(0001): Comparison of “first principles” theory with experiment

Luntz, A. C.; Persson, Mats; Wagner, Steffen; Frischkorn, Christian; Wolf, Martin

doi:10.1063/1.2206588

Cited by 79 publications

(164 citation statements)

References 33 publications

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“…This is for example the case when the electronic system is excited by a femtosecond laser 3,4 or hot electrons are produced with a metal-insulator-metal junction. 5 The Born-Oppenheimer approximation also breaks down if the time scales for the electronic and nuclear motions are comparable or if the separations between the electronic states are very small, such that transitions between the electronic states will occur.…”

Section: Introductionmentioning

confidence: 99%

Δself-consistent field method to obtain potential energy surfaces of excited molecules on surfaces

et al. 2008

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We present a modification of the ∆SCF method of calculating energies of excited states, in order to make it applicable to resonance calculations of molecules adsorbed on metal surfaces, where the molecular orbitals are highly hybridized. The ∆SCF approximation is a density functional method closely resembling standard density functional theory (DFT), the only difference being that in ∆SCF one or more electrons are placed in higher lying Kohn-Sham orbitals, instead of placing all electrons in the lowest possible orbitals as one does when calculating the ground state energy within standard DFT. We extend the ∆SCF method by allowing excited electrons to occupy orbitals which are linear combinations of Kohn-Sham orbitals. With this extra freedom it is possible to place charge locally on adsorbed molecules in the calculations, such that resonance energies can be estimated, which is not possible in traditional ∆SCF because of very delocalized Kohn-Sham orbitals. The method is applied to N2, CO and NO adsorbed on different metallic surfaces and compared to ordinary ∆SCF without our modification, spatially constrained DFT and inverse-photoemission spectroscopy (IPES) measurements. This comparison shows that the modified ∆SCF method gives results in close agreement with experiment, significantly closer than the comparable methods. For N2 adsorbed on ruthenium (0001) we map out a 2-dimensional part of the potential energy surfaces in the ground state and the 2π-resonance. From this we conclude that an electron hitting the resonance can induce molecular motion, optimally with 1.5 eV transferred to atomic movement. Finally we present some performance test of the ∆SCF approach on gas-phase N2 and CO, in order to compare the results to higher accuracy methods. Here we find that excitation energies are approximated with accuracy close to that of time-dependent density functional theory. Especially we see very good agreement in the minimum shift of the potential energy surfaces in the excited state compared to the ground state.

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Section: Introductionmentioning

confidence: 99%

Δself-consistent field method to obtain potential energy surfaces of excited molecules on surfaces

et al. 2008

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“…have recently been taken [3][4][5][6][7][8][9][10]. In contrast, the explicit description of e-h pair excitations and corresponding nonadiabatic couplings directly from first principles still poses a formidable challenge.In this regard, electronic friction theory (EFT) [11,12] has become a popular workhorse to effectively capture the effects of such nonadiabatic energy loss on the adsorbate dynamics in a computationally convenient way [13][14][15][16][17][18][19]. Inspired by vibrational lifetimes obtained via response theory [20] or Fermi's golden rule in the nuclear system [21], a Langevin equation for the nuclei emerges from a semiclassical picture implying complete electronic decoherence in terms of the Markov approximation [12].…”

mentioning

confidence: 99%

Nonadiabatic Vibrational Damping of Molecular Adsorbates: Insights into Electronic Friction and the Role of Electronic Coherence

2017

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We present a perturbation approach rooted in time-dependent density-functional theory to calculate electron-hole (e-h) pair excitation spectra during the nonadiabatic vibrational damping of adsorbates on metal surfaces. Our analysis for the benchmark systems CO on Cu(100) and Pt(111) elucidates the surprisingly strong influence of rather short electronic coherence times. We demonstrate how in the limit of short electronic coherence times, as implicitly assumed in prevalent quantum nuclear theories for the vibrational lifetimes as well as electronic friction, band structure effects are washed out. Our results suggest that more accurate lifetime or chemicurrentlike experimental measurements could characterize the electronic coherence. DOI: 10.1103/PhysRevLett.119.176808 The tortuous ways in which kinetic and chemical energy is transferred between adsorbates and substrate atoms fundamentally govern the dynamics of surface chemical reactions, for instance, in the context of heterogeneous catalysis or advanced deposition techniques. For metal substrates, the two main energy dissipation mechanisms in this regard are the adsorbate interaction with lattice vibrations, i.e., substrate phonons, and the excitation of electronhole (e-h) pairs. The latter are attributable to the nonadiabatic coupling of nuclear motion to the substrate electronic degrees of freedom (d.o.f.) and seem to be substantial in order to rationalize an increasing number of experimental findings [1,2]. Important steps towards an accurate, yet efficient firstprinciples-based modeling of the energy uptake into phononic d.o.f. have recently been taken [3][4][5][6][7][8][9][10]. In contrast, the explicit description of e-h pair excitations and corresponding nonadiabatic couplings directly from first principles still poses a formidable challenge.In this regard, electronic friction theory (EFT) [11,12] has become a popular workhorse to effectively capture the effects of such nonadiabatic energy loss on the adsorbate dynamics in a computationally convenient way [13][14][15][16][17][18][19]. Inspired by vibrational lifetimes obtained via response theory [20] or Fermi's golden rule in the nuclear system [21], a Langevin equation for the nuclei emerges from a semiclassical picture implying complete electronic decoherence in terms of the Markov approximation [12]. This approach thus avoids an explicit propagation of the electron dynamics and concomitant ultrafast time scales by coarse-graining the effects into electronic friction forces linear in nuclear velocities. This enables an efficient combination even with density-functional theory (DFT) based ab initio molecular dynamics (AIMD) simulations on high-dimensional potential energy surfaces as required for surface dynamical studies [15,22,23].Independent of the particular recipe employed to obtain the electronic friction coefficients [12,14,17,20,24,25], however, the downside of the coarse-graining of the electron dynamics is that it precludes a more fundamental understanding of the underlying e-h pair excit...

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“…That this is not the case has already been established[2] and a complete abinitio scheme for the electronic friction is needed. Such a scheme based on DFT has already been suggested and put to use within the Markov approximation[2, 19,21], but need to be generalized slightly to take memory effects into account. In section IV we will propose such a generalization.…”

Section: B Associative Desorption Of N2 From Ru(0001)mentioning

confidence: 99%

“…21, however, the dominating non-Markovian effect is the correlation function (13) which follows from the reduced density matrix formalism in conjunction with (19).…”

Section: Non-markovian Friction and Fluctuating Forces From Densimentioning

confidence: 99%

“…[18] At high electronic temperatures, thermal excitations dominate the electronic system and the Markov approximation is good for describing chemical reactions mediated by hot electrons. [19,20] However, for non-adiabatic dynamics in general, the Markov approximation may fail and it then becomes important to take into account the 'memory' of the system.…”

Section: Introductionmentioning

confidence: 99%

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Memory effects in nonadiabatic molecular dynamics at metal surfaces

Olsen

Schiøtz

2010

The Journal of Chemical Physics

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We study the effect of temporal correlation in a Langevin equation describing non-adiabatic dynamics at metal surfaces. For a harmonic oscillator the Langevin equation preserves the quantum dynamics exactly and it is demonstrated that memory effects are needed in order to conserve the ground state energy of the oscillator. We then compare the result of Langevin dynamics in a harmonic potential with a perturbative master equation approach and show that the Langevin equation gives a better description in the non-perturbative range of high temperatures and large friction. Unlike the master equation, this approach is readily extended to anharmonic potentials. Using density functional theory we calculate representative Langevin trajectories for associative desorption of N2 from Ru(0001) and find that memory effects lowers the dissipation of energy. Finally, we propose an ab-initio scheme to calculate the temporal correlation function and dynamical friction within density functional theory.

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Femtosecond laser induced associative desorption of H2 from Ru(0001): Comparison of “first principles” theory with experiment

Cited by 79 publications

References 33 publications

Δself-consistent field method to obtain potential energy surfaces of excited molecules on surfaces

Δself-consistent field method to obtain potential energy surfaces of excited molecules on surfaces

Nonadiabatic Vibrational Damping of Molecular Adsorbates: Insights into Electronic Friction and the Role of Electronic Coherence

Memory effects in nonadiabatic molecular dynamics at metal surfaces

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