Karnamohit's paper published in JCP!


Karnamohit's work studying size-dependent errors within the adiabatic approximation as seen in density based electron dynamics is now published in JCP! 

In this work we demonstrate the size-dependence of errors due to the use of real-time time-dependent density propagation as seen with Hartree-Fock (RT-TDHF) and RT-TDDFT within the adiabatic approximation.  We simulate electron-density dynamics with a set of three molecules exhibiting charge-transfer. We calculate the de-tuning of RT-TDHF Rabi frequencies and find decreasing discrepancy with linear response TDHF Rabi frequencies as the system-size increases. We also excite the system from the ground state into the excited state exhibiting charge-transfer and find that: 1. There is increased agreement with linear response theory predicted charge-transfer with system-size, and 2. Peak-shifts from the linear response frequencies in the absorption spectra decrease with increasing size. 

By comparing simulated electron dynamics and time-dependent electronic properties between RT-TDHF and time-dependent configuration-interaction with single-excitations (TD-CIS, a wave function method that does not suffer from the same problems as seen with RT-TDDFT and RT-TDHF) we show for the first time, to our knowledge, that such errors are mitigated as the system-size increases. We hope our study will serve as a basis for consideration of size-dependent effects when simulating electron dynamics of larger, realistic systems with time-dependent density-functional theory.