Quasi-Diabatic Scheme for Nonadiabatic On-the-Fly Simulations

Abstract

We use the quasi-diabatic (QD) propagation scheme to perform onthe-fly non-adiabatic simulations of the photodynamics of ethylene. The QD scheme enables a seamless interface between accurate diabatic-based quantum dynamics approaches and adiabatic electronic structure calculations, explicitly avoiding any efforts to construct global diabatic states or reformulate the diabatic dynamics approach to the adiabatic representation. Using partial linearized path-integral approach and symmetrical quasi-classical approach as the diabatic dynamics methods, the QD propagation scheme enables direct non-adiabatic simulation with the CASSCF on-the-fly electronic structure calculations. The population dynamics obtained from both approaches are in a close agreement with the quantum wavepacket based method and outperform the widely used trajectory surface hopping approach. Further analysis on the ethylene photodeactivation pathways demonstrates the correct predictions of competing processes of non-radiative relaxation mechanism through various conical intersections. This work provides the foundation of using accurate diabatic dynamics approaches and on-the-fly adiabatic electronic structure information to perform ab-initio non-adiabatic simulation.Non-adiabatic on-the-fly simulation | Quasi-Diabatic scheme | Diabatic dynamics approach | Path-integral methods

A molecular perspective on Tully models for nonadiabatic dynamics

“…59 The nonadiabatic dynamics of ethylene from its first excited singlet state has been the subject of numerous theoretical studies, employing a variety of approaches such as wavepacket propagation, 105 13 or the partial linearized path-integral and symmetrical quasi-classical approach within a quasi-diabatic propagation. 89 All methods predict a very similar behavior for the excited ethylene: after photoexcitation to the bright pp* state (S 1 ), internal conversion to the ground state occurs rapidly through two possible conical intersections. However, the ultrafast deactivation occurs in a Tully-I like manner, that is, the nuclear wavepacket only Fig.…”

“…86,87 Due to the negligible contribution of S 2 , only S 0 and S 1 were included in the nonadiabatic dynamics, as done in earlier works on ethylene. 88,89 The lowest four singlet states of DMABN were described with LR-TDDFT [90][91][92] within the Tamm-Dancoff approximation employing the LC-PBE functional 93,94 with a range-separation parameter set to 0.3 Bohr and the 6-31G basis set, using the Gaussian09 program. 95 For fulvene, the electronic structure quantities were computed using SA(2)-CASSCF(6/6)/ 6-31G* (including three pairs of p and p* orbitals in the active space).…”

“…Thanks to its straightforward dynamical behavior, ethylene has already been used in several studies to demonstrate the performance of on-the-fly nonadiabatic molecular dynamics methods, for example in ref.13, 88, 89 and 110. However, these benchmarks were not performed on a common set of initial conditions or using similar electronic structure methods, and with the exception of ref 89. have not been consistently compared to other nonadiabatic dynamics methods.The deactivation of ethylene from its S 1 state was simulated with the original TSH, decoherence-corrected TSH (dTSH, see computational details for more information), and AIMS, using a set of common initial conditions and the strategy discussed in Sections II.A.2 and II.A.3 for an improved comparison.…”

Nanosecond Photodynamics Simulations of a Cis-Trans Isomerization Are Enabled by Machine Learning

“…This pathway is consistent with prior theoretical studies on ethylene intramolecular hydrogen migration reactions. [24][25][26] Figure 10a shows this reaction pathway, Figure 10b and 10c show 208 QC and 1,344 ML-NAMD trajectories toward 2. A close look at the structural features of this pathway is shown in Figure 10d with 5 snapshots from trans-1-FC to 2, including the surface hopping point.…”

On-the-fly Symmetrical Quasi-classical Dynamics with Meyer-Miller Mapping Hamiltonian for the Treatment of Nonadiabatic Dynamics at Conical Intersections

“…Recently, Huo and coworkers proposed to employ the quasi-diabatization procedure in the 6 dynamics propagation. 88,[94][95][96][97] They used the quasi-diabatic basis to propagate the MM mapping…”