Atomistic studies of light driven electron dynamics are important in studies of photoactive materials. Spin resolved electronic structure calculations are necessary for transition metal, magnetic, and carbon materials, intermediates, and radicals. Most transition metal compounds exhibit open shell non-singlet configurations, necessitating separate treatment of electronic states with the alpha/beta spin components. Such approach describes a broader range of materials, identifies new channels of relaxation and charge transfer, and provides knowledge for rational design of materials in solar energy harvesting and information storage. A methodology, named spin resolved electron dynamics, uses spin polarized DFT as basis to implement non-adiabatic dynamics. At ambient temperatures, the thermal lattice vibrations facilitate non-adiabatic couplings and control the dissipative dynamics of the spin resolved density matrix.[1] Different initial excitations are analyzed and used to calculate relaxation dynamics. Spin resolved electronic dynamics is applied for studying vanadium (IV) substitutionally doped bulk anatase in a doublet ground state. The results show that a difference in electronic structure for alpha and beta spin components determines consequences in optical excitations and electronic dynamics pathways experienced by electrons with alpha and beta spin projections. Specifically, optical excitations involving occupied V 3d alpha orbital are responsible for IR-range absorption followed by nonradiative relaxation. Optical excitations in the visible range, involving orbitals of alpha spin component induce localization of a negative charge on the V ion for a long time period. The slower relaxation rate of alpha excitations is explained by larger subgaps to overcome compared to the ones experienced by similar excitations involving orbitals with beta projection of spin. For example, in majority of alpha excitations the hole is stalled at HOMO-1, an oxygen 2p state, during relaxation to HOMO, a vanadium 3d state. For initial excitations in the visible range, alpha and beta transitions are equally probable, causing competing processes within the system. It is anticipated this methodology can be broadly implemented on numerous transition metal applications, including optoelectronics, laser crystals, dyes, photovoltaic materials, and metal oxides for photo-electrochemical water splitting. [1] S. Jensen, D. Kilin, J. Phys.: Cond. Matt. 27(13), 134207 (2015).

Spin resolved electron dynamics of vanadium (IV) doped anatase

251st National Meeting (2016)

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