Loading...
Derniers dépôts, tout type de documents
The sinking of alkali cations in superfluid 4He nanodroplets is investigated theoretically using liquid 4He time-dependent density functional theory at zero temperature. The simulations illustrate the dynamics of the buildup of the first solvation shell around the ions. The number of helium atoms in this shell is found to linearly increase with time during the first stages of the dynamics. This points to a Poissonian capture process, as concluded in the work of Albrechtsen et al. on the primary steps of Na+ solvation in helium droplets [Albrechtsen et al., Nature 623, 319 (2023)]. The energy dissipation rate by helium atom ejection is found to be quite similar between all alkalis, the main difference being a larger energy dissipated per atom for the lighter alkalis at the beginning of the dynamics. In addition, the number of helium atoms in the first solvation shell is found to be lower at the end of the dynamics than at equilibrium for both Li+ and Na+, pointing to a kinetic rather than thermodynamical control of the snowball size for small and strongly attractive ions.
Interactions between molecular hydrogen and ions are of interest in cluster science, astrochemistry and hydrogen storage. In dynamical simulations, H2 molecules are usually modelled as point particles, an approximation that can fail for anisotropic interactions. Here, we apply an adiabatic separation of the H2 rotational motion to build effective pseudoatom-ion potentials and in turn study the properties of (H2)nNa+/Cl− clusters. These interaction potentials are based on high-level ab initio calculations and Improved Lennard-Jones parametrizations, while the subsequent dynamics has been performed by quantum Monte Carlo calculations. By comparisons with simulations explicitly describing the molecular rotations, it is concluded that the present adiabatic model is very adequate. Interestingly, we find differences in the cluster stabilities and coordination shells depending on the spin isomer considered (para- or ortho-H2), especially for the anionic clusters.
Recent experiments have shown that translational energy loss is mainly mediated by electron–hole pair excitations for hydrogen atoms impinging on clean metallic surfaces. Inspired by these studies, quasi-classical trajectory simulations are here performed to investigate the energy transfer after scattering of hydrogen atoms off clean and hydrogen-covered tungsten (100) surfaces. The present theoretical approach examines the coverage effect of the preadsorbed hydrogen atoms, as was done recently for the (110) crystallographic plane in (J Phys Chem C 125:14075, 2021). As suggested, scattering can be described in terms of three different dynamical mechanisms, the contribution of which changes with coverage, which allow to rationalize the shape of the energy loss spectra.
We present quasi-classical trajectory calculations of the F + HCl reactive scattering, for total angular momentum equal zero and using a London–Eyring–Polanyi–Sato potential energy surface specifically developed for the title reaction. The reactive dynamics is investigated for a wide range of collision energies, from subthermal velocities up to kinetic energies significantly exceeding the dissociation energy of the reactant molecule. We focus here on the light- and heavy-atom exchange probability and mechanisms at hyperthermal collision velocities, whereas low-energy collisions (which dominate the evaluation of the reaction rate constant) are used for the purpose of validating the current implementation of the quasi-classical trajectory method in a symmetrical hyperspherical configuration space. In spite of the limitations of the potential energy surface, the present methodology yields reaction probabilities in agreement with previous experimental and theoretical results. The computed branching probabilities among the different reaction channels exhibit a mild dependence on the initial vibrational state of the diatomic molecule. Conversely, they show a marked sensitivity to the value of the impact angle, which becomes more pronounced for increasing collision energies.
The triatomic system NeI2 is studied under the consideration that the diatom is found in an excited electronic state (B). The vibrational levels (v=13, …, 23) are considered within two well-known theoretical procedures: quasi-classical trajectories (QCT), where the classical equations of motion for nuclei are solved on a single potential energy surface (PES), and the trajectory surface hopping (TSH) method, where the same are solved in a bunch of crossed vibrational PES (diabatic representation). The trajectory surface hopping fewest switches (TSHFS) is implemented to minimize the number of hoppings, thus allowing the calculations of hopping probability between the different PES's, and the kinetic mechanism to track the dissociation path. From these calculations, several observables such as, the lifetimes, vibrational and rotational energies (I2), dissociation channels, are obtained. Our results are compared with previous experimental and theoretical work.
Sujets
Electron transfer
DIFFERENTIAL CROSS-SECTIONS
ELECTRON DYNAMICS
Collisions des atomes
Calcium
Dynamique quantique
COHERENT CONTROL
ENTANGLEMENT
Dynamique non-adiabatique
Rydberg atoms
Agrégats
Dissipative quantum methods
Atom
Coordonnées hypersphériques elliptiques
Cesium
Collisions ultra froides
Ejection
Close-coupling
Atomic clusters
Slow light
Ultrashort pulses
Effets transitoires
Electron-surface collision
Ab initio calculations
Anisotropy
CAVITY
Dynamique moléculaire quantique
Dynamics
Contrôle cohérent
Non-equilibrium Green's function
Collision frequency
Clusters
Alkali-halide
Propagation effects
Ab-initio
4He-TDDFT simulation
Bohmian trajectories
DRIVEN
Atomic collisions
Fonction de Green hors-équilibre
DISSIPATION
Electric field
Théorie de la fonctionnelle de la densité
CONICAL INTERSECTION
Quantum dynamics
DEMO
Dissipation
COLLISION ENERGY
Transport électronique
MODEL
Effets de propagation
Theory
Density functional theory
Cryptochrome
Photophysics
Deformation
Dynamique mixte classique
Muonic hydrogen
Effets inélastiques
WAVE-PACKET DYNAMICS
Composés organiques à valence mixte
Drops
ALGORITHM
MCTDH
Effets isotopiques
Half revival
Cosmological constant
Dissipative dynamics
STATE
Anharmonicity
Cope rearrangement
Atomic scattering from surfaces
Coulomb presssure
ELECTRONIC BUBBLE FORMATION
Classical trajectory
ENERGY
DFTB
ELECTRON-NUCLEAR DYNAMICS
Wave packet interferences
QUANTUM OPTIMAL-CONTROL
DENSITY
CLASSICAL TRAJECTORY METHOD
Cluster
AR
ENTROPY
Transitions non-adiabatiques
DEPENDENT SCHRODINGER-EQUATION
Diels-Alder reaction
Coherent control
Dark energy
Superfluid helium nanodroplets
Electronic transport inelastic effects
Extra dimension
Casimir effect
CHEMICAL-REACTIONS
Electronic Structure
COMPLEX ABSORBING POTENTIALS
Molecules
Tetrathiafulvalene
DYNAMICS