Multiconfigurational time-dependent Hartree study of complex dynamics: Photodissociation of NO2

Abstract

The multiconfigurational time-dependent Hartree (MCTDH) approach is applied to an example showing very complex dynamics: the wave-packet dynamics on the three-dimensional B2 potential-energy surface of NO2. The ability of the MCTDH scheme to describe accurately the severe splitting of the wave packet on a saddle-shaped surface is demonstrated. Internal checks of the MCTDH calculation enable us to assess the degree of convergence without the need to resort to a numerically exact wave-packet calculation. As a representative observable the photodissociation spectrum is calculated and discussed. The A1/B2 vibronic coupling is neglected in our study, but the dynamics on the diabatic B2 surface is treated in its full three dimensionality.

Photoionization of hydrogen atoms by coherent intense high-frequency short laser pulses: Direct propagation of electron wave packets on large spatial grids

“…There are also weak field calculations for two electrons on relatively large (up to ∼ 10 3 Bohr) radial grids [28], but these are still 10 times smaller than the grid sizes needed here in the case of intense fields. Alternatively, the multi-configuration timedependent Hartree (MCTDH) method [29,30] could be used which is known to be an optimal approach for wave packet propagation in many degrees of freedom. Clearly, this approach requires efficient propagation algorithms for the underlying single-particle time-dependent functions [31].…”

Semiclassical on-the-fly computation of the S→S1 absorption spectrum of formaldehyde

“…6 A main obstacle is the need for a global potential energy surface ͑PES͒ without which one cannot implement quantum dynamics methods such as the multiconfiguration time-dependent Hartree approach. 7 It is therefore appealing to devise on-the-fly dynamics methods which need only local force field information as input. For ground electronic state dynamics this is implemented by using classical mechanics as an approximation for the quantum dynamics.…”

An extension of the grid empowered molecular simulator to quantum reactive scattering

“…The basic outcome of these two programs is the scattering S matrix from which reaction probabilities, cross sections, and rate coefficients can be derived. More detailed More demanding has been the work needed to extend GEMS to include the MCTDH-FC code [9,10] (see the leftmost box of the dynamics block of Figure 1). In the MCTDH method, the nuclear TD Schrödinger equation is solved for multidimensional dynamical systems consisting of distinguishable particles using the Dirac Frenkel variational method.…”

“…As most quantum dynamics treatments, the method suffers from the exponential scaling problem. [9] Fortunately, the base to be exponentiated is substantially smaller compared with the standard methods and this allows the treatment of somewhat larger systems or more structured wavepackets. In the limit of convergence with respect to the number of configurations, in fact, the results of a MCTDH propagation are numerically exact and, even in this limit, the equations of motion, although seemingly complex, require less effort than the standard methods for large systems.…”

“…[9,10] The article is structured as follows. In An overview of theoretical and computational approaches to quantum reactive problems section, an overview on the theoretical and computational machinery developed in COST D37 to the end of extending GEMS to quantum methods is given.…”