Effects of electronic relaxation processes on vibrational linewidths of adsorbates on surfaces: The case of CO/Cu(100)

Novko, Dino; Alducin, M.; Blanco-Rey, M.; Juaristi, J. I.

doi:10.1103/physrevb.94.224306

Cited by 34 publications

(65 citation statements)

References 95 publications

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“…An emblematic example is the IS mode of CO on Cu(100). Even if its relaxation is considered to be mostly nonadiabatic [2,24], the corresponding vibrational linewidths calculated recently with ab initio firstorder perturbation theory are significantly lower than the experimental values [25,26]. This discrepancy together with the indisputable evidence for the intermode coupling in CO/Cu(100) [5,14] points out to an overlooked relaxation mechanism that should incorporate both the nonadiabatic and intermode couplings on the same footing.…”

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confidence: 87%

“…State-of-the-art theory.-Thus far the vibrational relaxation of molecules at metal surfaces was studied mostly by means of the (first-order) Fermi's golden rule formula (i.e., by only considering the terms ∝ g 2 , where g is the electron-phonon matrix element) [15-18, 25, 27-29]. An analogous pathway in many-body perturbation theory (MBPT) is to calculate the phonon self-energy due to electron-phonon coupling up to first order, π [1] λ (q, ω) (λ, q, and ω are the index, momentum, and energy of the phonon mode, respectively) [26]. The corresponding phonon linewidth is obtained by taking the imaginary part of π [1] λ , i.e., γ [1] qλ = −2Im π [1] λ (q, ω qλ ).…”

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confidence: 99%

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Electron-Mediated Phonon-Phonon Coupling Drives the Vibrational Relaxation of CO on Cu(100)

2018

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We bring forth a consistent theory for the electron-mediated vibrational intermode coupling that clarifies the microscopic mechanism behind the vibrational relaxation of adsorbates on metal surfaces. Our analysis points out the inability of state-of-the-art nonadiabatic theories to quantitatively reproduce the experimental linewidth of the CO internal stretch mode on Cu(100) and it emphasizes the crucial role of the electron-mediated phonon-phonon coupling in this regard. The results demonstrate a strong electron-mediated coupling between the internal stretch and low-energy CO modes, but also a significant role of surface motion. Our nonadiabatic theory is also able to explain the temperature dependence of the internal stretch phonon linewidth, thus far considered a sign of the direct anharmonic coupling.

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confidence: 87%

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confidence: 99%

Electron-Mediated Phonon-Phonon Coupling Drives the Vibrational Relaxation of CO on Cu(100)

2018

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“…This practice corresponds to departing from the strict zero-frequency limit by averaging over nonadiabatic coupling contributions away from the Fermi level. 57 Recently, Zin and Subotnik have put forward an alternative method to calculate EFT practically based on interpolation. 58 The EFT calculations are performed using the all-electron, local atomic orbital code FHI-aims.…”

Section: Theorymentioning

confidence: 99%

Symmetry-Adapted High Dimensional Neural Network Representation of Electronic Friction Tensor of Adsorbates on Metals

2019

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Nonadiabatic effects in chemical reaction at metal surfaces, due to excitation of electron-hole pairs, stand at the frontier of the studies of gas-surface reaction dynamics.However, the first principles description of electronic excitation remains challenging.In an efficient molecular dynamics with electronic friction (MDEF) method, the nonadiabatic couplings are effectively included in a so-called electronic friction tensor (EFT), which can be computed from first-order time-dependent perturbation theory (TDPT) in terms of density functional theory (DFT) orbitals. This second-rank tensor depends on adsorbate position and features a complicated transformation with regard to the intrinsic symmetry operations of the system. In this work, we develop a new symmetry-adapted neural network representation of EFT, based on our recently proposed embedded atom neural network (EANN) framework. Inspired by the derivation of the nonadiabatic coupling matrix, we represent the tensorial friction by the first and second derivatives of multiple outputs of NNs with respect to atomic Cartesian coordinates. This rigorously preserves the positive semidefiniteness, directional property, and correct symmetry-equivariance of EFT. Unlike previous methods, our new approach can readily include both molecular and surface degrees of freedom, regardless of the type of surface. Tests on the H2+Ag(111) system show that this approach yields an accurate, efficient, and continuous representation of EFT, making it possible to perform large scale TDPT-based MDEF simulations to study both adiabatic and nonadiabatic energy dissipation in a unified framework.

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“…Finally, I stress that the presented theoretical framework is quite general and can be employed in other interesting cases where electron relaxation processes are expected to be decisive. For instance, it could help elucidate the processes responsible for the large broadening of the E 2g phonon in highly doped graphene [12] or graphite [6], as well as for the anomalous temperature behavior of hexagonal-close-packed transition metals [41].Within the many-body perturbation theory, the NA phonon properties are usually extracted from the phonon propagator [3,13,42],where q and ν are the phonon momentum and band index, respectively, ω A qν is the adiabatic phonon fre-arXiv:1806.03212v2 [cond-mat.mtrl-sci]…”

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Nonadiabatic coupling effects in MgB2 reexamined

Novko

2018

Phys. Rev. B

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The unusual Raman spectrum of MgB2 and its formidable temperature dependence are successfully reproduced by means of a parameter-free ab initio nonadiabatic theory that accounts for the electron-hole pair scattering mechanisms with the system phonons. This example turns out to be a prototypical case where a strong nonadiabatic renormalization of the phonon frequency is partially washed out by the aforementioned scattering events, bringing along a characteristic temperature dependence. Both electron-hole pair lifetime and energy renormalization effects due to dynamical electron-phonon coupling turn out to play a crucial role. This theory could aid in comprehending other Raman spectra characterized with unconventionally strong electron-phonon interaction.Recent years have witnessed an ample interest in nonadiabatic (NA) coupling effects [1,2] and their intriguing impact on the vibrational properties of solids [3]. Particularly strong deviations from the adiabatic phonon spectrum were observed for the long wavelength (q ≈ 0) modes of carbon-based materials, such as metallic carbon nanotubes [4,5], graphite intercalation compounds [6-9], graphene [10][11][12], and boron-doped diamond [13]. The corresponding NA theory based in first principles is well established and in most instances the calculated NA phonon frequencies complement the experiments quite accurately [6,10,14]. Remarkably, in MgB 2 , both the state-of-the-art adiabatic and NA descriptions break down. Namely, the Raman measurements reveal an unusually large linewidth of the E 2g phonon peaked at around 77 meV [15][16][17][18][19], which falls just between the adiabatic (67 meV) and NA (94 meV) values [6,14].In order to resolve this discrepancy numerous explanations emerged. A significant temperature dependence of the phonon spectrum lead numerous studies to ascribe the foregoing anomalies to the anharmonicity [20][21][22][23][24]. Conversely, it was shown that the phonon-phonon corrections constitute only a small portion of the E 2g phonon linewidth and the frequency shift, as well as bring about a minor temperature change [16,[25][26][27][28]. The effects of the electron relaxation processes (e.g., higher order electron-phonon scattering) on the phonon spectrum were also taken into consideration, since it was shown that high-frequency optical modes in metallic systems might be rather sensitive to these processes when q ≈ 0 [29][30][31][32][33][34][35]. In fact, few studies have qualitatively demonstrated that it is precisely this mechanism that prompts the breakdown of the standard adiabatic and NA theories in MgB 2 [6,16,19,27,36,37]. Nevertheless, a concomitant NA theory based in first principles that can resolve this controversy is still absent. Such an in-depth quantitative survey of the NA effects is of great fundamental interest, e.g., for comprehending superconductivity mechanisms, especially in MgB 2 , * dino.novko@gmail.com where the unusually strong interaction between the E 2g phonon and electrons is suspected to underly the electron pairing p...

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Effects of electronic relaxation processes on vibrational linewidths of adsorbates on surfaces: The case of CO/Cu(100)

Cited by 34 publications

References 95 publications

Electron-Mediated Phonon-Phonon Coupling Drives the Vibrational Relaxation of CO on Cu(100)

Electron-Mediated Phonon-Phonon Coupling Drives the Vibrational Relaxation of CO on Cu(100)

Symmetry-Adapted High Dimensional Neural Network Representation of Electronic Friction Tensor of Adsorbates on Metals

Nonadiabatic coupling effects in MgB2 reexamined

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