Nonadiabatic dynamics applications

One can also ask about the relationship of the FMS method, as opposed to AIMS, with other wavepacket and semiclassical nonadiabatic dynamics methods. We first compare FMS to previous methods in cases where there is no spawning, and then proceed to compare with previous methods for nonadiabatic dynamics. We stress that we have always allowed for spawning in our applications of the method, and indeed the whole point of the FMS method is to address problems where localized nuclear quantum mechanical effects are important. Nevertheless, it is useful to place the method in context by asking how it relates to previous methods in the absence of its adaptive basis set character. There have been many attempts to use Gaussian basis functions in wavepacket dynamics, and we cannot mention all of these. Instead, we limit ourselves to those methods that we feel are most closely related to FMS, with apologies to those that are not included. A nice review that covers some of the... 

Finally, we discuss applications of the ZPE-corrected mapping formalism to nonadiabatic dynamics induced by avoided crossings of potential energy surfaces. Figure 27 shows the diabatic and adiabatic electronic population for Model IVb, describing ultrafast intramolecular electron transfer. As for the models discussed above, it is seen that the MFT result (y = 0) underestimates the relaxation of the electronic population while the full mapping result (y = 1) predicts a too-small population at longer times. In contrast to the models... 

Following a brief introduction of the basic concepts of semiclassical dynamics, in particular of the semiclassical propagator and its initial value representation, we discuss in this section the application of the semiclassical mapping approach to nonadiabatic dynamics. Based on numerical results for the... 

Summary. An effective scheme for the laser control of wavepacket dynamics applicable to systems with many degrees of freedom is discussed. It is demonstrated that specially designed quadratically chirped pulses can be used to achieve fast and near-complete excitation of the wavepacket without significantly distorting its shape. The parameters of the laser pulse can be estimated analytically from the Zhu-Nakamura (ZN) theory of nonadiabatic transitions. The scheme is applicable to various processes, such as simple electronic excitations, pump-dumps, and selective bond-breaking, and, taking diatomic and triatomic molecules as examples, it is actually shown to work well. 

Improved and extended versions of this conical intersection model involving four or seven nuclear degrees of freedom have been developed. Raab et al. extended these vibronic-coupling models to include all 24 normal modes of pyrazine. These models have served as testbeds for the development and application of novel techniques for the treatment of multi-dimensional nonadiabatic dynamics. 

The mapping procedure introduced in Sec. 6 results in a quantum-mechanical Hamiltonian with a well-defined classical limit, and therefore extends the applicability of the established semiclassical approaches to nonadiabatic dynamics. The thus obtained semiclassical version of the mapping approach, as well as the equivalent formulation that is obtained by requantizing the classical electron analog model of Meyer and Miller, have been applied to a variety of systems with nonadiabatic dynamics in the recent years. It appears that this approach is so far the only fully semiclassical method that allows a numerical treatment of truly multidimensional nonadiabatic dynamics at conical intersections. 

Let us suppose it is possible to treat the nuclear subsystem in a molecule classically and electronic subsystem quantum mechanically. This type of theoretical framework is called a mixed quantum-classical representation. Such a mixed representation can find many applications in science. For instance, a fast mode such as the proton dynamics in a protein should be considered as a quantum subsystem, while the rest of the skeletal structure can be treated as a classical subsystem [3, 484, 485]. It is quite important in this context to establish the correct equations of motion for each of the subsystems and to ask what are their rigorous solutions and how the quantum effects penetrate into the classical subsystems. By studying the quantum-electron and classical-nucleus nonadiabatic dynamics as deeply as possible, we will see how such rigorous solutions, if any, look like qualitatively and quantitatively. This is one of the main aims of this book. 

This section follows the above basic theory and method of path-branching representation of nonadiabatic dynamics with numerical examples. We also show the performance of the semiclassical Ehrenfest theory to compare with. What we present below is illustrative numerical realization rather than optimized practice for actual applications. 

The following subsections are devoted to illustrative applications of nona-diabatic electron wavepacket dynamics to chemical reactions. By tuning pulse laser fields in a coherent or incoherent sense, one can significantly modulate the electronic transition and subsequent molecular dynamics. The correlation between the nonadiabatic term and laser fields can lead to dramatic change in chemical dynamics, which implies that nonadiabatic dynamics and intense-laser fields should be treated on an equal footing [425, 491, 492, 494], Below we show those examples of the coupling between nonadiabatic interactions and laser fields. 

Abstract We present a general theoretical approach for the simulation and control of ultrafast processes in complex molecular systems. It is based on the combination of quantum chemical nonadiabatic dynamics on the fly with the Wigner distribution approach for simulation and control of laser-induced ultrafast processes. Specifically, we have developed a procedure for the nonadiabatic dynamics in the framework of time-dependent density functional theory using localized basis sets, which is applicable to a large class of molecules and clusters. This has been combined with our general approach for the simulation of time-resolved photoelectron spectra that represents a powerful tool to identify the mechanism of nonadiabatic processes, which has been illustrated on the example of ultrafast photodynamics of furan. Furthermore, we present our field-induced surface hopping (FISH) method which allows to include laser fields directly into the nonadiabatic... 

Application of the Nonadiabatic Dynamics on the fly for the Simulation of Ultrafast Observables of Furan Comparison with Experiment... 

The full dynamical treatment of electrons and nuclei together in a laboratory system of coordinates is computationally intensive and difficult. However, the availability of multiprocessor computers and detailed attention to the development of efficient software, such as ENDyne, which can be maintained and debugged continually when new features are added, make END a viable alternative among methods for the study of molecular processes. Eurthemiore, when the application of END is compared to the total effort of accurate determination of relevant potential energy surfaces and nonadiabatic coupling terms, faithful analytical fitting and interpolation of the common pointwise representation of surfaces and coupling terms, and the solution of the coupled dynamical equations in a suitable internal coordinates, the computational effort of END is competitive. 

B. H. Lengsfield and D. R. Yarkony, Nonadiabatic Interactions Between Potential Energy Surfaces Theory and Applications, in State-Selected and State to State Ion-Molecule Reaction Dynamics Part 2 Theory, M. Baer and C.-Y. Ng, eds., John Wiley Sons, Inc., New York, 1992, Vol, 82, pp. 1-71. 

Lengsfield BH, Yarkony DR (1992) Nonadiabatic interactions between potential energy surfaces theory and applications. In Baer M, Ng CY (eds) State-selected and state-to-state ion-molecule reaction dynamics part 2 theory, Vol. 82 of Advances in Chemical Physics, John Wiley and Sons, New York, p 1-71. 

In this chapter, we are concerned with various theoretical formulations that allow us to treat nonadiabatic quantum dynamics in a classical description. To introduce the main concepts, we first give a brief overview of the existing methods and then discuss their application to ultrafast molecular photoprocesses. 

Because the mapping approach treats electronic and nuclear dynamics on the same dynamical footing, its classical limit can be employed to study the phase-space properties of a nonadiabatic system. With this end in mind, we adopt a onemode two-state spin-boson system (Model IVa), which is mapped on a classical system with two degrees of freedom (DoF). Studying various Poincare surfaces of section, a detailed phase-space analysis of the problem is given, showing that the model exhibits mixed classical dynamics [123]. Furthermore, a number of periodic orbits (i.e., solutions of the classical equation of motion that return to their initial conditions) of the nonadiabatic system are identified and discussed [125]. It is shown that these vibronic periodic orbits can be used to analyze the nonadiabatic quantum dynamics [126]. Finally, a three-mode model of nonadiabatic photoisomerization (Model III) is employed to demonstrate the applicability of the concept of vibronic periodic orbits to multidimensional dynamics [127]. 

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