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Soutenance de thèse de Lei Shi (6 déc)
par - 11 novembre 2023
Theoretical Study of the Hydrogen atom Scattering from a Graphene Surface
This research thesis focuses on classical and quantum molecular dynamics simulations, specifically investigating the scattering of hydrogen atoms from a graphene surface. Graphene, a two-dimensional crystal composed of carbon atoms, holds great promise for diverse applications in astrophysics, hydrogen storage, and semiconductor manufacturing. The thesis delves into the study of graphene, a hydrogenated form of graphene that possesses a tunable bandgap suitable for electronic applications. Through experimental studies and simulations, the thesis explores the adsorption of hydrogen atoms on the graphene surface, the formation of C-H chemical bonds, and the energy transfer occurring during collisions between hydrogen atoms and graphene. To unravel the quantum effects inherent in this system, the thesis proposes quantum dynamics (QD) simulations based on prior research on H atom scattering from graphene surfaces. These simulations incorporate the probabilistic wave functions that characterize the quantum mechanical nature of particles. However, QD simulations present computational challenges due to their high-dimensional nature and complex calculations. To address these challenges, the thesis introduces the Multi-Configuration Time-Dependent Hartree (MCTDH) method, an influential approach for simulating complex quantum systems. It highlights the multilayer formulation of MCTDH (ML-MCTDH), which extends the number of degrees of freedom that can be handled. The computational complexities of QD simulations are mitigated by transforming the Potential Energy Surface (PES) into a Sum of Products (SOP) form, thereby reducing the computational demands. The thesis outlines the strategies employed to overcome the computational complexity and memory requirements of the 75-dimensional QD simulations. It discusses the implementation of a newly devised flux momentum operator and presents a novel benchmark of classical molecular dynamics (cMD) simulations. Furthermore, it demonstrates the progression from dimensionreduced systems to the full-dimensional system, providing a comprehensive examination and exploration of classical and quantum molecular dynamics simulations.