Extending the Applicability of the Multiple-Spawning Framework for Nonadiabatic Molecular Dynamics

Abstract

Ab initio multiple-spawning (AIMS) describes the nonadiabatic dynamics of molecules by expanding nuclear wave functions in a basis of traveling multidimensional Gaussians called trajectory basis functions (TBFs). New TBFs can be spawned whenever nuclear amplitude is transferred between electronic states due to nonadiabatic transitions. While the adaptive size of the TBF basis grants AIMS its characteristic accuracy in describing nonadiabatic processes, it also leads to a fast and uncontrolled growth of the number of TBFs, penalizing computational efficiency. A different flavor of AIMS, called AIMS with informed stochastic selections (AIMSWISS), has recently been proposed to reduce the number of TBFs dramatically. Herein, we test the performance of AIMSWISS for a series of challenging nonadiabatic processesphotodynamics of two-dimensional model systems, 1,2-dithiane and chromium (0) hexacarbonyland show that this method is robust and extends the range of molecular systems that can be simulated within the multiple-spawning framework.

What Controls the Quality of Photodynamical Simulations? Electronic Structure Versus Nonadiabatic Algorithm

“…AIMSWISS combines AIMS with the stochastic selection idea inherent to TSH, resulting in a method that lies between the two. The advantage of the AIMSWISS method is often AIMS-quality results for a cost close to TSH . More advanced techniques for coupled electron–nuclear dynamics then exploit the time-dependent variational principle to drive the nuclear wave functions, e.g., the dd-vMCG method. , These approaches are already highly demanding and require a gradual buildup of a semianalytical potential energy surface .…”

Probing the sensitivity of ab initio multiple spawning to its parameters

“…We note that a stochastic-selection version of AIMS naturally alleviates the possible issues related to this parameter as unnecessary TBFs in the dynamics are automatically detected and stochastically discarded. [57,[62][63][64] FIG. 7.…”

Recombination of N Atoms in a Manifold of Electronic States Simulated by Time-Reversed Nonadiabatic Photodissociation Dynamics of N2

“…Even for the simpler diatomic molecules, there is a maze of higher energy excited electronic states . High resolution spectroscopy has made major steps in understanding the structure of the stationary states. , But the dynamics of these states is still a subject of active research; see, for example, the literature − and, of course, the very elegant attosecond studies of H 2 and HD and their ions. , There have been corresponding developments in theoretical and computational dynamics. − Two dimensional and higher order spectroscopy has also made significant contributions. , Laser methods − have enabled a detailed analysis of what are the exit channels. Toward these developments, we discuss a complementary computational approach to photodissociation dynamics.…”