arXiv subjects

Maite Alducin

Publications and source records attributed to Maite Alducin.

17 recordsLinked to original sources

arXiv2025

Interplay between electronic and phononic energy dissipation channels in the adsorption of CO on Cu(110)

In this work, we investigate the relative importance of electronic and phononic energy dissipation during the molecular adsorption of CO on Cu(110). Initial sticking probabilities as a function of impact energy for CO impinging at normal incidence at a surface temperature of 90 K were computed using classical trajectory simulations. To this aim, we use a full-dimensional potential energy surface constructed using an atomistic neural network trained on density functional theory data obtained with the nonlocal vdW-DF2 exchange-correlation functional. Two models are compared: one allowing only energy transfer and dissipation from the molecule to lattice vibrations, and the other also incorporating the effect of molecular energy loss due to the excitation of electron-hole pairs, modeled within the local-density friction approximation. Our results reveal, firstly, that the molecule mainly transfers energy to lattice vibrations, and this channel determines the adsorption probabilities, with electronic friction playing a minor role. Secondly, once the molecule is trapped near the surface (where electronic density is higher), electron-hole pair excitations accelerate energy dissipation, significantly promoting CO thermalization. Still, the faster energy dissipation when electron-hole pair excitations are accounted for accelerates the accommodation of the adsorbed molecules in the chemisorption well but does not significantly alter their lateral displacements over the surface.

cond-mat.mtrl-sci↗

arXiv2025

Ab initio insights into plasmonic and strong-field contributions to H$_2$ dissociation on silver nanoshells

Modeling plasmonic catalysis by applying femtosecond laser pulses of high intensity ($10^{13}-10^{15}$ W cm$^{-2}$), although justified by the time-dependent density functional theory (TDDFT) time-scale limitations, can lead to a dissociation mechanism that is completely unrelated to the plasmon excitation created under low-intensity continuous light in experiments (on the order of 1 W cm$^{-2}$). In this study, we examine the dissociation of H$_2$ on a large octahedral Ag nanoshell under varying field intensity, frequency, and duration, and we explore the possibility of identifying optimal modeling conditions accessible with current TDDFT simulations. We show that using this large nanoshell that consists in the outer layer of the Ag$_{231}$ cluster, it is still possible to disentangle the role of the plasmon from strong-field effects at applied field intensities as high as $(2-8) \times 10^{13}$ W cm$^{-2}$. In particular, although strong-field effects are always present at these intensities, we find that the excited plasmon dominates the dissociation process at the lowest applied intensity of $2 \times 10^{13}$ W cm$^{-2}$. Furthermore, at the highest intensity, at which strong-field effects become dominant, the plasmon contributes to accelerating the dissociation of the molecule. Overall, our simulations pave the way to bridge the intensity gap between TDDFT modeling and experiments in plasmonic catalysis.

physics.chem-ph↗

arXiv2025

Asymmetry and coverage dependence in two-pulse correlation measurements of CO photodesorption from Pd(111): Insights from theory

Two-pulse correlation experiments performed using pulses of different intensities on Pd(111) with different CO coverages showed that the CO photodesorption probability depends on whether the strong or the weak pulse arrives first to the surface, being this difference particularly large for the low-covered surface. Motivated by these experiments, we perform molecular dynamics simulations using a multicoverage potential energy surface that was previously constructed with the embedded atom neural network method. The process is modeled by combining the two-temperature model (2TM)--to describe the laser-excited electrons and phonons--and Langevin dynamics with electronic time-dependent temperature $T_\textrm{e}$--to model the coupling of the nuclei degrees of freedom with the laser-excited electrons. We show that improving the energy balance description in 2TM--by including \textit{ab-initio} $T_\textrm{e}$-dependent electronic heat capacity and electron-phonon coupling constant--is key to reproduce the asymmetry of the photodesorption probability $P_{\rm des}$ between positive and negative time delays. Furthermore, we also explore possible reasons for the usual underestimation of $P_{\rm des}$ at zero delay given by state-of-the-art calculations. In particular, we improve the description of the energy exchange between CO and the metal surface at high $T_\textrm{e}$ by including in the simulations a $T_\textrm{e}$-dependent friction coefficient. The prediction for $P_{\rm des}$ at zero delay in this case, increases by an order of magnitude, reducing its discrepancy with the experimental value. Altogether, our results hint to the importance of accounting for the temperature dependence of the electronic structure and properties in describing the extreme conditions generated in 2PC experiments.

physics.chem-ph↗

arXiv2025

Dynamic Training Enhances Machine Learning Potentials for Long-Lasting Molecular Dynamics

Molecular Dynamics (MD) simulations are vital for exploring complex systems in computational physics and chemistry. While machine learning methods dramatically reduce computational costs relative to ab initio methods, their accuracy in long-lasting simulations remains limited. Here we propose dynamic training (DT), a method designed to enhance accuracy of a model over extended MD simulations. Applying DT to an equivariant graph neural network (EGNN) on the challenging system of a hydrogen molecule interacting with a palladium cluster anchored to a graphene vacancy demonstrates a superior prediction accuracy compared to conventional approaches. Crucially, the DT architecture-independent design ensures its applicability across diverse machine learning potentials, making it a practical tool for advancing MD simulations.

cond-mat.mtrl-sci↗

arXiv2024

Scattering of CO from Vacant-MoSe$_2$ with O Adsorbates: Is CO$_2$ Formed?

Using ab initio molecular dynamics (AIMD) simulations, based on density functional theory that also accounts for van der Waals interactions, we study the oxidation of gas phase CO on MoSe$_2$ with a Se vacancy and oxygen coverage of 0.125~ML. In the equilibrium configuration, one of the O atoms is adsorbed on the vacancy and the other one atop one Se atom. Recombination of the CO molecule with the second of these O atoms to form CO$_2$ is a highly exothermic reaction, with an energy gain of around 3~eV. The likeliness of the CO oxidation reaction on this surface is next examined by calculating hundreds of AIMD trajectories for incidence energies that suffice to overcome the energy barriers in the entrance channel of the CO oxidative recombination. In spite of it, no CO$_2$ formation event is obtained. In most of the calculated trajectories the incoming CO molecule is directly reflected and in some cases, mainly at low energies, the molecules remain trapped at the surface but without reacting. As important conclusion, our AIMD simulations show that the recombination of CO molecules with adsorbed O atoms is a very unlikely reaction in this system, despite its large exothermicity.

physics.chem-ph↗

arXiv2024

Strong-field effects in the photo-induced dissociation of the hydrogen molecule on a silver nanoshell

Plasmonic catalysis is a rapidly growing field of research, both from experimental and computational perspectives. Experimental observations demonstrate an enhanced dissociation rate for molecules in the presence of plasmonic nanoparticles under low-intensity visible light. The hot-carrier transfer from the nanoparticle to the molecule is often claimed as the mechanism for dissociation. However, the charge transfer time scale is on the order of few femtoseconds and cannot be resolved experimentally. In this situation, ab initio non-adiabatic calculations can provide a solution. Such simulations, however, have their own limitations related to the computational cost. To accelerate plasmonic catalysis simulations, many researchers resort to applying high-intensity external fields to nanoparticle-molecule systems. Here, we show why such an approach can be problematic and emphasize the importance of considering strong-field effects when interpreting the results of time-dependent density functional theory simulations of plasmonic catalysis. By studying the hydrogen molecule dissociation on the surface of a silver nanoshell and analyzing the electron transfer at different field frequencies and high intensities, we demonstrate that the molecule dissociates due to multiphoton absorption and subsequent ionization.

physics.chem-ph↗

arXiv2024

Hydrogen abstraction from metal surfaces: When electron-hole pair excitations strongly affect hot-atom recombination

Using molecular dynamics simulations, we predict that the inclusion of nonadiabatic electronic excitations influences the dynamics of preadsorbed hydrogen abstraction from the W(110) surface by hydrogen scattering. The hot-atom recombination, which involves hyperthermal diffusion of the impinging atom on the surface, is significantly affected by the dissipation of energy mediated by electron-hole pair excitations at low coverage and low incidence energy. This issue is of importance as this abstraction mechanism is thought to largely contribute to molecular hydrogen formation from metal surfaces.

cond-mat.mtrl-sci↗

arXiv2023

Vibrational dynamics of CO on Pd(111) in and out of thermal equilibrium

Using many-body perturbation theory and density functional perturbation theory, we study the vibrational spectra of the internal stretch (IS) mode of CO on Pd(111) for the bridge and hollow adsorption structures that are experimentally identified at 0.5~ML coverage. Our theoretical treatment allows us to determine the temperature dependence of the IS vibrational spectra under thermal conditions as well as the time evolution of the non-equilibrium transient spectra induced by femtosecond laser pulses. Under thermal conditions (i.e., for equal electronic $T_e$ and phononic $T_l$ temperatures), the calculated lifetimes at 10-150~K are mostly due to nonadiabatic couplings (NC), i.e., first-order electronic excitations. As temperature increases, also the contribution of the second-order electron mediated phonon-phonon couplings (EMPPC) progressively increases from 25\% at low temperatures to 50\% at 300~K. Our calculations for the laser-induced non-equilibrium conditions comprise experimental absorbed fluences of 6-130~J/m$^2$. For fluences for which $T_e>$2000~K, the transient vibrational spectra are characterized by two different regimes that follow the distinct time-evolution of $T_e$ and $T_l$ and are respectively dominated by NC and EMPPC processes. At lower fluences, the initial fast regime becomes progressively negligible as $T_e$ decreases and only the steady second regime remains visible. Qualitatively, all these spectral properties are common to the both adsorption structures studied here.

cond-mat.mtrl-sci↗

arXiv2023

Photo-Induced CO Desorption Dominates over Oxidation on Different O+CO Covered Ru(0001) Surfaces

The photo-induced desorption and oxidation of CO on Ru(0001) is simulated using ab initio molecular dynamics with electronic friction that accounts for the non-equilibrated excited electrons and phonons. Different (O,CO) coverages are considered, the experimental room temperature coverage consisting in 0.5ML-O+0.25ML- CO (low coverage), the saturation coverage achieved experimentally at low temperatures (0.5ML-O+0.375ML-CO, intermediate coverage), and the equally mixed monolayer that is stable according to our calculations but not experimentally observed yet (0.5ML-O+0.5ML-CO, high coverage). The results of our simulations for the three coverages are consistent with femtosecond laser experiments showing that the CO photo-desorption largely dominates over CO photo-oxidation. These results cannot be explained in terms of the distinct activation energies calculated for the relaxed surfaces. Different (dynamical) factors such as the coupling to the laser-excited electrons and, more importantly, the interadsorbate energy exchange and the strong surface distortions induced in the more crowded surfaces are fundamental to understand the competition between these two processes under the extremely non-equilibrated conditions created by the laser.

cond-mat.mtrl-sci↗

arXiv2023

Anomalous transient blueshift in the internal stretch mode of CO/Pd(111)

In time-resolved pump-probe vibrational spectroscopy the internal stretch mode of polar molecules is utilized as a key observable to characterize the ultrafast dynamics of adsorbates on surfaces. The adsorbates non-adiabatic intermode couplings are the commonly accepted mechanisms behind the observed transient frequency shifts. Here, we study the CO/Pd(111) system with a robust theoretical framework that includes electron-hole pair excitations and electron-mediated coupling between the vibrational modes. A mechanism is revealed that screens the electron-phonon interaction and originates a blueshift under ultrafast non-equilibrium conditions. The results are explained in terms of the abrupt change in the density of states around the Fermi level, and are instrumental for understanding dynamics at multi-component surfaces involving localized and standard $s$ or $p$ states.

cond-mat.mtrl-sci↗

arXiv2022

Adsorption and dissociation of diatomic molecules in monolayer $1H$-MoSe$_2$

Two dimensional transition metal dichalcogenides appear as good candidates for gas sensing and catalysis. Here, by means of density functional theory, we characterize the adsorption and dissociation of selected diatomic molecules (CO, H$_2$, O$_2$, and NO) on the MoSe$_2$ monolayer. We consider that these processes occur on the pristine $1H$-MoSe$_2$ monolayer and in the vicinity of an isolated Se vacancy. The presence of Se vacancies both enhances the molecular adsorption and reduces the energy needed for dissociation, making it energetically favorable for the case of O$_2$ and NO molecules. For each case we evaluate the effect that each adsorbate has on the electronic structure of the MoSe$_2$ monolayer and the charge transfer that takes place between the adsorbate and the surface. Remarkably, adsorption of either CO or NO at the Se vacancy induces a finite spin-magnetization in the system that is spatially well localized around the adsorbate and the three closest Mo atoms.

cond-mat.mtrl-sci↗

arXiv2021

O$_2$ on Ag(110): A puzzle for exchange-correlation functionals

Despite the great success of density functional theory in describing materials, there are still a few examples where current exchange-correlation functionals fail. We add another example to this list that drives further development of functionals. We show that the interaction of O$_2$ with Ag(110) cannot be properly described by some of the most popular GGA, meta GGA, and hybrid functionals. We identify problems and provide clues for a functional that should be able to describe this and similar systems properly.

cond-mat.mtrl-sci↗

arXiv2021

Insights into the Coadsorption and Reactivity of O and CO on Ru(0001) and Their Coverage Dependence

Using density functional theory and an exchange-correlationfunctional that includes the van der Waals interaction, we study the coadsorption of CO on Ru(0001) saturated with 0.5 ML of oxygen. Different coexisting CO coverages are considered that are experimentally motivated, the room temperaturecoverage consisting of 0.5 ML-O + 0.25 ML-CO (low coverage), the saturation coverage achieved at low temperatures (0.5 ML-O + 0.375 ML-CO, intermediate coverage), and the equally mixed monolayer that is stable according to our calculations but not experimentally observed yet (0.5 ML-O + 0.5 ML-CO, high coverage). For each coverage, we study the competition between the desorption and oxidation of CO on the corresponding optimized structure by analyzing their reaction energies and minimum energy reaction paths. The desorption process is endothermic at all coverages, although the desorption energy decreases as the CO coverage increases. The process itself (and also the reverted adsorption) becomes more involved at the intermediate and high coverages because of the appearance of a physisorption well and concomitant energy barrier separating it from the chemisorbed state. Remarkably, the oxidation of CO, which is endothermic at low coverages, turns exothermic at the intermediate and high coverages. In all cases, the minimum reaction path for oxidation, which involves the chemisorbed and physisorbed CO2, is ruled by one of the large energy barriers that protect these molecular states. Altogether, the larger activation energies for oxidation as compared to those for desorption and the extreme complexity of the oxidation against the desorption paths explain that CO desorption dominates over the oxidation in experiments.

cond-mat.mtrl-sci↗

arXiv2019

Adiabatic and Nonadiabatic Energy Dissipation during Scattering of Vibrationally Excited CO from Au(111)

A high-dimensional potential energy surface (PES) for CO interaction with the Au(111) surface is developed using a machine-learning algorithm. Including both molecular and surface coordinates, this PES enables the simulation of the recent experiment on scattering of vibrationally excited CO from Au(111). Trapping in a physisorption well is observed to increase with decreasing incidence energy. While energy dissipation of physisorbed CO is slow, due to weak coupling with both the phonons and electron-hole pairs, its access to the chemisorption well facilitates fast vibrational relaxation of CO through nonadiabatic coupling with surface electron-hole pairs.

physics.chem-ph↗

arXiv2018

Electron-mediated phonon-phonon coupling drives the vibrational relaxation of CO on Cu(100)

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.

cond-mat.mtrl-sci↗

arXiv2013

Ready, set and no action: A static perspective on potential energy surfaces commonly used in gas-surface dynamics

In honoring the seminal contribution of Henry Eyring and Michael Polanyi who first introduced the concept of potential energy surfaces (PESs) to describe chemical reactions in gas-phase [Z. Phys. Chem. 12, 279-311, (1931)], this work comes to review and assess state-of-the-art approaches towards first-principle based modeling in the field of gas-surface dynamics. Within the Born-Oppenheimer and frozen surface approximations, the O2-Ag(100) interaction energetics are used as a showcase system to accentuate the complex landscape exhibited by the PESs employed to describe the impingement of diatomics on metal substrates and draw attention to the far-from-trivial task of continuously representing them within all six molecular degrees of freedom. To this end, the same set of ab initio reference data obtained within Density Functional Theory (DFT) are continuously represented by two different state-of-the-art high-dimensional approaches, namely the Corrugation-Reducing Procedure and Neural Networks. Exploiting the numerically undemanding nature of the resulting representations, a detailed static evaluation is performed on both PESs based on an extensive global minima search. The latter proved particularly illuminating in revealing representation deficiencies which affect the dynamical picture yet go otherwise unnoticed within the so-called "divide-and-conquer" approach.

cond-mat.mtrl-sci↗

arXiv2012

Non-adiabatic effects during the dissociative adsorption of O2 at Ag(111)? A first-principles divide and conquer study

We study the gas-surface dynamics of O2 at Ag(111) with the particular objective to unravel whether electronic non-adiabatic effects are contributing to the experimentally established inertness of the surface with respect to oxygen uptake. We employ a first-principles divide and conquer approach based on an extensive density-functional theory mapping of the adiabatic potential energy surface (PES) along the six O2 molecular degrees of freedom. Neural networks are subsequently used to interpolate this grid data to a continuous representation. The low computational cost with which forces are available from this PES representation allows then for a sufficiently large number of molecular dynamics trajectories to quantitatively determine the very low initial dissociative sticking coefficient at this surface. Already these adiabatic calculations yield dissociation probabilities close to the scattered experimental data. Our analysis shows that this low reactivity is governed by large energy barriers in excess of 1.1 eV very close to the surface. Unfortunately, these adiabatic PES characteristics render the dissociative sticking a rather insensitive quantity with respect to a potential spin or charge non-adiabaticity in the O2-Ag(111) interaction. We correspondingly attribute the remaining deviations between the computed and measured dissociation probabilities primarily to unresolved experimental issues with respect to surface imperfections.

cond-mat.mtrl-sci↗