arXiv subjects

Alberto S. Muzas

Publications and source records attributed to Alberto S. Muzas.

4 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

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↗

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

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↗