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Taleb AA, Schiller F, Vyalikh DV, María Pérez J, Auras SV, Farías D, Ortega JE. Simulating high-pressure surface reactions with molecular beams. Phys Chem Chem Phys 2024; 26:1770-1776. [PMID: 38168970 DOI: 10.1039/d3cp05071h] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2024]
Abstract
Using a reactive molecular beam with high kinetic energy (Ekin), it is possible to speed gas-surface reactions involving high activation barriers (Eact), which would require elevated pressures (P0) if a random gas with a Maxwell-Boltzmann distribution is used. By simply computing the number of molecules that overcome the activation barrier in a random gas at P0 and in a molecular beam at Ekin = Eact, we establish an Ekin-P0 equivalence curve, through which we postulate that molecular beams are ideal tools to investigate gas-surface reactions that involve high activation energies. In particular, we foresee the use of molecular beams to simulate gas surface reactions within the industrial-range (>10 bar) using surface-sensitive ultra-high vacuum (UHV) techniques, such as X-ray photoemission spectroscopy (XPS). To test this idea, we revisit the oxidation of the Cu(111) surface combining O2 molecular beams and XPS experiments. By tuning the kinetic energy of the O2 beam in the range of 0.24-1 eV, we achieve the same sequence of surface oxides obtained in ambient pressure photoemission (AP-XPS) experiments, in which the Cu(111) surface was exposed to a random O2 gas up to 1 mbar. We observe the same surface oxidation kinetics as in the random gas, but with a much lower dose, close to the expected value derived from the equivalence curve.
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Affiliation(s)
- Amjad Al Taleb
- Facultad de Ciencias, Universidad Autónoma de Madrid, 28049 Cantoblanco Madrid, Spain
| | - Frederik Schiller
- Centro de Física de Materiales CSIC/UPV-EHU-Materials Physics Center, E-20018 San Sebastián, Spain.
| | - Denis V Vyalikh
- Donostia International Physics Center, E-20018 Donostia-San Sebastián, Spain
- IKERBASQUE, Basque Foundation for Science, 48013, Bilbao, Spain
| | - José María Pérez
- Facultad de Ciencias, Universidad Autónoma de Madrid, 28049 Cantoblanco Madrid, Spain
| | - Sabine V Auras
- Centro de Física de Materiales CSIC/UPV-EHU-Materials Physics Center, E-20018 San Sebastián, Spain.
- Universidad del País Vasco, Dpto. Física Aplicada, E-20018 San Sebastián, Spain
| | - Daniel Farías
- Facultad de Ciencias, Universidad Autónoma de Madrid, 28049 Cantoblanco Madrid, Spain
- Instituto "Nicolás Cabrera", Universidad Autónoma de Madrid, 28049 Madrid, Spain
- Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | - J Enrique Ortega
- Centro de Física de Materiales CSIC/UPV-EHU-Materials Physics Center, E-20018 San Sebastián, Spain.
- Donostia International Physics Center, E-20018 Donostia-San Sebastián, Spain
- Universidad del País Vasco, Dpto. Física Aplicada, E-20018 San Sebastián, Spain
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Töpfer K, Upadhyay M, Meuwly M. Quantitative molecular simulations. Phys Chem Chem Phys 2022; 24:12767-12786. [PMID: 35593769 PMCID: PMC9158373 DOI: 10.1039/d2cp01211a] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2022] [Accepted: 04/30/2022] [Indexed: 11/21/2022]
Abstract
All-atom simulations can provide molecular-level insights into the dynamics of gas-phase, condensed-phase and surface processes. One important requirement is a sufficiently realistic and detailed description of the underlying intermolecular interactions. The present perspective provides an overview of the present status of quantitative atomistic simulations from colleagues' and our own efforts for gas- and solution-phase processes and for the dynamics on surfaces. Particular attention is paid to direct comparison with experiment. An outlook discusses present challenges and future extensions to bring such dynamics simulations even closer to reality.
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Affiliation(s)
- Kai Töpfer
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland.
| | - Meenu Upadhyay
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland.
| | - Markus Meuwly
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland.
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Al Taleb A, Farías D. Phonon dynamics of graphene on metals. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2016; 28:103005. [PMID: 26886508 DOI: 10.1088/0953-8984/28/10/103005] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The study of surface phonon dispersion curves is motivated by the quest for a detailed understanding of the forces between the atoms at the surface and in the bulk. In the case of graphene, additional motivation comes from the fact that thermal conductivity is dominated by contributions from acoustic phonons, while optical phonon properties are essential to understand Raman spectra. In this article, we review recent progress made in the experimental determination of phonon dispersion curves of graphene grown on several single-crystal metal surfaces. The two main experimental techniques usually employed are high-resolution electron energy loss spectroscopy (HREELS) and inelastic helium atom scattering (HAS). The different dispersion branches provide a detailed insight into the graphene-substrate interaction. Softening of optical modes and signatures of the substrate's Rayleigh wave are observed for strong graphene-substrate interactions, while acoustic phonon modes resemble those of free-standing graphene for weakly interacting systems. The latter allows determining the bending rigidity and the graphene-substrate coupling strength. A comparison between theory and experiment is discussed for several illustrative examples. Perspectives for future experiments are discussed.
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Affiliation(s)
- Amjad Al Taleb
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, 28049 Madrid, Spain
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