Ultrafast nonadiabatic relaxation of C₆₀ with decoherence: DFT versus extended tight-binding model

Nonadiabatic relaxation of photoabsorbed fullerene materials are relevant in electron transport and cooling processes. In this work, we use an approach of electron-phonon coupled nonadiabatic molecular dynamics (NAMD) [1] to simulate the relaxation of molecular C₆₀. The methodology relies on a combination of the fewest-switch surface hopping approach and Kohn−Sham single-particle description in density functional theory (DFT) [2]. In this scheme, when nuclear wavefunctions for different electronic states sufficiently separate, the quantum mechanical coherence between the components of electronic wavepackets should cease to exit creating a decoherence condition [3], the effect of which is not clearly known for C₆₀. We will present the results of the femtosecond evolution of various excited and intermediate states by including this decoherence effect. We will further compare the results of PBE exchange-correlation functional in DFT with rather inexpensive extended tight-binding model (xTB) [4]. The success of the xTB approach will provide a cheaper option to study fullerene-based larger systems. [1] M. Madjet et al., Phys. Rev. Lett. 126, 183002, (2021); [2] A V. Akimov and O.V Prezhdo, J. Chem. Theory Comput. 9, 11 (2013); [3] J. Kang and L.-W. Wang, Phys. Rev. B 99, 224303 (2019); [4] C. Bannwarth et al., Comp. Mol. Sc. 11, 1493 (2021).