Phonon-induced Spin State Relaxation in spin crossover molecule*

Spin crossover (SCO) materials have drawn intense attention lately due to its unique property to switch from low-spin to high-spin state by external stimuli. The relaxation time of the spin state is a critical quantity in all application areas. Whether SCO molecules are in solution or in crystal form, it is crucial to understand the spin dynamics of a single molecule. This study describes a method development that goes beyond our previous work¹ on phonon-assisted electron relaxation processes where the total spin of the system remains unchanged. We discuss using spin-orbit coupling instead of kinetic energy of nuclei as a perturbation between states of different total spins. This method considers different nuclear positions in the configuration space generated by ab-initio molecular dynamics, which provides a suitable description for coupling between the vibrational modes of nuclei and the electron spins. We will demonstrate the dynamics of spin-dependent relaxation using our simulations

1 J. P. Trinastic et al. J. Phys. Chem. C, 119, 2015.