Modeling Fast Electron Dynamics with Real-Time Time-Dependent Density Functional Theory: Application to Small Molecules and Chromophores

Abstract

The response of matter to external fields forms the basis for a vast wealth of fundamental physical processes ranging from light harvesting to nanoscale electron transport. Accurately modeling ultrafast electron dynamics in excited systems thus offers unparalleled insight but requires an inherently nonlinear time-resolved approach. To this end, an efficient and massively parallel real-time real-space time-dependent density functional theory (RT-TDDFT) implementation in NWChem is presented. The implementation is first validated against linear-response TDDFT and experimental results for a series of molecules subjected to small electric field perturbations. Second, nonlinear excitation of green fluorescent protein is studied, which shows a blue-shift in the spectrum with increasing perturbation, as well as a saturation in absorption. Next, the charge dynamics of optically excited zinc porphyrin is presented in real time and real space, with relevance to charge injection in photovoltaic devices. Finally, intermolecular excitation in an adenine-thymine base pair is studied using the BNL range separated functional [ Baer , R. ; Neuhauser , D. Phys. Rev. Lett. 2005 , 94 , 043002 ], demonstrating the utility of a real-time approach in capturing charge transfer processes.

Engineering and manipulating exciton wave packets

“…While standard DFT is a ground state theory, RT-TDDFT allows electron density to dynamically respond to laser irradiation 34,35 . Inter-and intra-site electron interactions, a manifold of energy levels, and temporally varying electronic orbitals with a complex spatial character are all captured within this computational paradigm which has been successfully applied to study excited-state electron dynamics [36][37][38] . density functional theory (RT-TDDFT) is…”

Efficient electron dynamics with the planewave-based real-time time-dependent density functional theory: Absorption spectra, vibronic electronic spectra, and coupled electron-nucleus dynamics

“…40 Numerical methods to solve the above TDKS equation have been studied based on various quantum computational codes. [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] However, the details are quite different depending on the basis sets. In this paper, we focus on the PW-based code.…”

“…[4][5][6][7][8][9][10][11] However, it is limited to investigate the response of electron density beyond the linear response, according to the applied perturbation, and can be described regardless of the strength of the perturbation. To this end, the real-time time-dependent density functional theory (RT-TDDFT), [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] a real-time approach in TDDFT regime, 27 is proposed to investigate the "real" electron dynamics according to the applied external field.…”

“…[12][13][14][15] For the case of atomic orbital basis sets, many researchers have studied excited state properties by using their house-made real-time electron dynamics program. [20][21][22][23][24][25][26] Chen et al have implemented classical electrodynamics coupled to quantum electron dynamics, and obtained absorption spectra of a silver nanoparticle absorbed with a molecule. 21 Lopata et al have developed massively parallel RT-TDDFT method and investigated the electron dynamics of an excited zinc porphyrin.…”

“…21 Lopata et al have developed massively parallel RT-TDDFT method and investigated the electron dynamics of an excited zinc porphyrin. 22 Also, there are many efforts to couple the motion of nuclei to electron dynamics. 26,27 Even though there are many efforts to implement the RT-TDDFT on various density functional theory (DFT)-based programs, the faster and accurate numerical time evolution is always important for the practical RT-TDDFT.…”