Quantum Effects in the Diffusion of Hydrogen on Ru(0001)

McIntosh, E. M.; Wikfeldt, Kjartan Thor; Ellis, John; Michaelides, Angelos; Allison, W.

doi:10.1021/jz400622v

Cited by 63 publications

(70 citation statements)

References 48 publications

(92 reference statements)

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“…Quantum effects were found to be significant at temperatures as high as 200 K, while for T < 120 K a tunneling-dominated temperatureindependent motion was observed, with a large jump rate of ∼ 10 9 s −1 . The crossover to tunneling-dominated diffusion at low temperatures was well reproduced by the QTST calculations, but the tunneling rate turned out to be underestimated when compared with experimental data 236 . Even though superfluidity in bulk molecular hydrogen has not been observed, reduction of dimensionality has been regarded as a possible way for the detection of a superfluid phase at low temperatures.…”

Section: Surfaces and Adsorbatesmentioning

confidence: 77%

Path-integral simulation of solids

Herrero

Ramı́rez

2014

J. Phys.: Condens. Matter

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The path-integral formulation of the statistical mechanics of quantum many-body systems is described, with the purpose of introducing practical techniques for the simulation of solids. Monte Carlo and molecular dynamics methods for distinguishable quantum particles are presented, with particular attention to the isothermal-isobaric ensemble. Applications of these computational techniques to different types of solids are reviewed, including noble-gas solids (helium and heavier elements), group-IV materials (diamond and elemental semiconductors), and molecular solids (with emphasis on hydrogen and ice). Structural, vibrational, and thermodynamic properties of these materials are discussed. Applications also include point defects in solids (structure and diffusion), as well as nuclear quantum effects in solid surfaces and adsorbates. Different phenomena are discussed, as solid-to-solid and orientational phase transitions, rates of quantum processes, classical-to-quantum crossover, and various finite-temperature anharmonic effects (thermal expansion, isotopic effects, electron-phonon interactions). Nuclear quantum effects are most remarkable in the presence of light atoms, so that especial emphasis is laid on solids containing hydrogen as a constituent element or as an impurity.

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Section: Surfaces and Adsorbatesmentioning

confidence: 77%

Path-integral simulation of solids

Herrero

Ramı́rez

2014

J. Phys.: Condens. Matter

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“…But there are plenty of cases, e.g. the spectrum of liquid water, [3][4][5] hydrogen-diffusion on metals, 6,7 and proton/hydride-transfer reactions, [8][9][10][11][12][13] for which one needs to evaluate time-correlation functions of the form 1 Z C AB (t) = 1…”

Section: Introductionmentioning

confidence: 99%

Boltzmann-conserving classical dynamics in quantum time-correlation functions: “Matsubara dynamics”

Hele

Willatt

Muolo

et al. 2015

The Journal of Chemical Physics

108

224

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We show that a single change in the derivation of the linearized semiclassical-initial value representation (LSC-IVR or 'classical Wigner approximation') results in a classical dynamics which conserves the quantum Boltzmann distribution. We rederive the (standard) LSC-IVR approach by writing the (exact) quantum time-correlation function in terms of the normal modes of a free ring-polymer (i.e. a discrete imaginary-time Feynman path), taking the limit that the number of polymer beads N → ∞, such that the lowest normal-mode frequencies take their 'Matsubara' values. The change we propose is to truncate the quantum Liouvillian, not explicitly in powers of 2 at 0 (which gives back the standard LSC-IVR approximation), but in the normalmode derivatives corresponding to the lowest Matsubara frequencies. The resulting 'Matsubara' dynamics is inherently classical (since all terms O( 2 ) disappear from the Matsubara Liouvillian in the limit N → ∞), and conserves the quantum Boltzmann distribution because the Matsubara Hamiltonian is symmetric with respect to imaginary-time translation. Numerical tests show that the Matsubara approximation to the quantum timecorrelation function converges with respect to the number of modes, and gives better agreement than LSC-IVR with the exact quantum result. Matsubara dynamics is too computationally expensive to be applied to complex systems, but its further approximation may lead to practical methods.

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“…Moreover, the structural, dynamic, and electronic properties of water are known to be heavily affected by the quantum nature of the nuclei even at room temperature [7][8][9][10][11][12][13][14] . In fact, nuclear quantum effects (NQE) have also been shown, through several experiments and a few theoretical works, to play a crucial role in the behaviour of organic adsorbates on metallic surfaces [15][16][17][18][19][20][21][22][23][24] . It is thus to be expected that both conformational entropy and nuclear quantum contributions impact the physics underlying the processes of water adsorption and dissociation on metallic surfaces.…”

Section: Introductionmentioning

confidence: 99%

Decisive role of nuclear quantum effects on surface mediated water dissociation at finite temperature

Litman

Donadio

Ceriotti

et al. 2017

The Journal of Chemical Physics

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Water molecules adsorbed on inorganic substrates play an important role in several technological applications. In the presence of light atoms in adsorbates, nuclear quantum effects (NQE) influence the structural stability and the dynamical properties of these systems. In this work, we explore the impact of NQE on the dissociation of water wires on stepped Pt(221) surfaces. By performing ab initio molecular dynamics simulations with van der Waals corrected density functional theory, we note that several competing minima for both intact and dissociated structures are accessible at finite temperatures, making it important to assess whether harmonic estimates of the quantum free energy are sufficient to determine the relative stability of the different states. We thus perform ab initio path integral molecular dynamics (PIMD) in order to calculate these contributions taking into account conformational entropy and anharmonicities at finite temperatures. We propose that when when adsorption is weak and NQE on the substrate are negligible, PIMD simulations can be performed through a simple partition of the system, resulting in considerable computational savings. We then calculate the full contribution of NQE to the free energies, including also anharmonic terms. We find that they result in an increase of up to 20% of the quantum contribution to the dissociation free energy compared to the harmonic estimates. We also find that the dissociation process has a negligible contribution from tunneling, but is dominated by ZPE, which can enhance the rate of dissociation by three orders of magnitude. Finally we highlight how both temperature and NQE indirectly impact dipoles and the redistribution of electron density, causing work function to changes of up to 0.4 eV with respect to static estimates. This quantitative determination of the change in work function provides a possible approach to determine experimentally the most stable configurations of water oligomers on the stepped surfaces.

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Quantum Effects in the Diffusion of Hydrogen on Ru(0001)

Cited by 63 publications

References 48 publications

Path-integral simulation of solids

Path-integral simulation of solids

Boltzmann-conserving classical dynamics in quantum time-correlation functions: “Matsubara dynamics”

Decisive role of nuclear quantum effects on surface mediated water dissociation at finite temperature

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