NEXMD v2.0 Software Package for Nonadiabatic Excited State Molecular Dynamics Simulations

Abstract

We present NEXMD version 2.0, the second release of the NEXMD (Nonadiabatic EXcited-state Molecular Dynamics) software package. Across a variety of new features, NEXMD v2.0 incorporates new implementations of two hybrid quantum-classical dynamics methods, namely, Ehrenfest dynamics (EHR) and the Ab-Initio Multiple Cloning sampling technique for Multiconfigurational Ehrenfest quantum dynamics (MCE-AIMC or simply AIMC), which are alternative options to the previously implemented trajectory surface hopping (TSH) method. To illustrate these methodologies, we outline a direct comparison of these three hybrid quantum-classical dynamics methods as implemented in the same NEXMD framework, discussing their weaknesses and strengths, using the modeled photodynamics of a polyphenylene ethylene dendrimer building block as a representative example. We also describe the expanded normal-mode analysis and constraints for both the ground and excited states, newly implemented in the NEXMD v2.0 framework, which allow for a deeper analysis of the main vibrational motions involved in vibronic dynamics. Overall, NEXMD v2.0 expands the range of applications of NEXMD to a larger variety of multichromophore organic molecules and photophysical processes involving quantum coherences and persistent couplings between electronic excited states and nuclear velocity.

Machine Learning Framework for Modeling Exciton Polaritons in Molecular Materials

“…We chose the azomethane molecule to demonstrate implementation of the approach described above. The training data are generated with the open source NEXMD package ,, following the common NAMD procedure. The semiempirical Austin model 1 (AM1) and configuration interaction singles (CIS) are chosen for the electronic structure simulations.…”

Twisting Aromaticity and Photoinduced Dynamics in Hexapole Helicenes

“…Nonadiabatic Excited-State Molecular Dynamics . Nonadiabatic EXcited-state Molecular Dynamics (NEXMD) ,, is a computational package developed for on-the-fly simulation of photoexcited dynamics in large molecules using a variety of mixed quantum-classical methods. Herein, the modified Fewest Switches Surface Hopping (FSSH) algorithm is used to model the excited-state dynamics in the C 1 ( P,M,P,M,M,P ), C 2 ( P,M,P,P,M,P ), and D 3 ( P,M,P,M,P,M ) isomers of the hexapole [5]­helicene (Figure ).…”

“…These properties can ultimately influence their efficacy in minimizing energy dissipation and achieving wavelength specificity in optoelectronic devices. The size of these systems and the complexity of their photophysics involving multiple coupled excited states necessitate the utilization of hybrid quantum-classical methodologies, , enabling on-the-fly atomistic nonadiabatic molecular dynamics simulations. − Herein, we use the NEXMD software package ,, specifically developed to perform such simulations in large conjugated molecules with a manifold of coupled electronic excited states. NEXMD has been previously used to model nanorings, nanobelts, and related contorted polycyclic aromatics with different symmetries, − suggesting that it is suitable for the analysis of the energy relaxation and redistribution in these molecular families.…”

Potential energy interpolation with target-customized weighting coordinates: application to excited-state dynamics of photoactive yellow protein chromophore in water

“…Nonadiabatic molecular dynamics (NAMD) simulation has become one of the crucial tools to investigate photo-induced processes in diverse chemical systems. Together with the continuing efforts in theoretical developments 1–5 and recently achieved code implementations, 6–15 performing NAMD simulations for molecules in complex environments has now become more of a routine task than ever before. The task always calls for the use of a multistate potential energy surface (PES), and in the majority of simulation efforts, PES information has been obtained in a direct manner with on-the-fly evaluations of electronic structures practically at each and every conformation visited during the simulations.…”