Molecular Dynamics

Charutz, D. M. ; Baer, R. ; Baer, M. A study of degenerate vibronic coupling effects on scattering processes: Are resonances affected by degenerate vibronic coupling?. Chem. Phys. Lett. 1997, 265, 629–637.Abstract

Recently the Jahn-Teller model was extended to treat (reactive) scattering processes. The present study is devoted to possible effects of a degenerate vibronic coupling (DVC) on resonances. The main conclusions are: (a) The DVC affects dramatically the state-to-state transition processes and as a result it shuffles resonances attached to given transitions and may cause existing resonances to be masked by other processes. (b) The DVC may affect the widths and the heights of resonances but change only slightly their position.

Baer, R. ; Zeiri, Y. ; Kosloff, R. Hydrogen transport in nickel (111). Phys. Rev. B 1997, 55, 10952. baer1997e.pdf
Citri, O. ; Baer, R. ; Kosloff, R. The role of non adiabatic mechanisms in the dissociation dynamics of O2 on silver surfaces. Surf. Sci. 1996, 351, 24–42.Abstract

The dissociation dynamics of oxygen on silver surfaces is studied theoretically. The method is based on a quantum-mechanical time-dependent non-adiabatic picture. A universal functional form for the potential energy surfaces is employed. The diabatic potentials describing the sequence of events leading to dissociation begin from the physisorption potential crossing over to a charged molecular chemisorption potential and crossing over again to the dissociated atomic-surface potential. Within such a potential surface topology, two different surfaces leading to dissociation are studied: the empirical potential of Spruit and the ab-initio potential of Nakatsuji. It is found that the system is captured by the molecular chemisorption well for a considerable length of time, long enough for thermalization. Thus the calculation is split into two parts: the calculation of “direct” dissociation probability and the calculation of nonadiabatic dissociative tunneling rate from the thermalized chemisorbed molecular state. For the direct probabilities, the Fourier method with the Chebychev polynomial expansion of the evolution operator is used to solve the time-dependent Schrödinger equation. For the tunneling rate calculation, a similar expansion of Green's operator is used. The output of the direct-reaction calculation is the dissociation probability as a function of the initial energy content, while the tunneling calculation yields the dissociation rate. The dependence of the direct dissociation probability on the initial kinetic energy is found to be non-monotonic. A strong isotope effect has been found, favoring the dissociation of the light species.

Baer, R. ; Zeiri, Y. ; Kosloff, R. Influence of dimensionality on deep tunneling rates: A study based on the hydrogen-nickel system. Phys. Rev. B 1996, 54, R5287.
Katz, G. ; Baer, R. ; Kosloff, R. A new method for numerical flux calculations in quantum molecular dynamics. Chem. Phys. Lett. 1995, 239, 230–236.Abstract

The flux of an evolving wavepacket is the definite time integral of its probability current density. A new method for calculating the flux, based on a Chebychev polynomial expansion of the quantum evolution operator is presented. The central point of the development is that the time integration of the current density is performed analytically, resulting in a scheme which eliminates additional numerical errors. Using this method, one benefits from both the time-dependent and time-independent frameworks of the dynamics. Furthermore, the method requires only a small modification to the existing Chebychev polynomial evolution code. Examples of performance and accuracy and an application to the calculation of recombinative desorption probabilities of N2 on Re are shown and discussed.

Saalfrank, P. ; Baer, R. ; Kosloff, R. Density matrix description of laser-induced hot electron mediated photodesorption of NO from Pt (111). Chem. Phys. Lett. 1994, 230, 463–472.