Quantum Dissipative Dynamics (QDD): A real-time real-space approach to far-off-equilibrium dynamics in finite electron systems

The Exact Exchange-Correlation Potential in Time-Dependent Density Functional Theory: Choreographing Electrons with Steps and Peaks

“…XC [n(t)](r) which can be a useful analysis tool in cases where the exact groundstate xc potential can be computed (usually model 1D systems). Due to the lack of memory, the adiabatic approximation leads to large errors in some applications, sometimes failing completely [52][53][54][55][56][57][58][59][60], but in other cases it has been found to yield good predictions [5][6][7][8][9][10][11][12][13][14][15][16][17][18], even when the system is far from a ground-state. It is not completely understood why: possible reasons include, that the adiabatic approximation satisfies a number of exact conditions that are important in the time-dependent case [2], that in some applications a strong external field dominates over xc effects in driving the dynamics and that partial compensation of selfinteraction in the Hartree potential, even at the groundstate level, is enough, especially when the observables involve averaging over the details of the density distribution.…”

“…1(a) and 2(a), a = 1, the 50:50 superposition. In exact TDDFT, the density of this interacting state as a function of time n(r, t) = 1 1 + |a| 2 n 0 (r) + |a| 2 n 1 (r) + 2an 01 (r) cos(ωt) (11) where n q (r) = 2 |Ψ q (r, r 2 )| 2 d 3 r 2 , q = 0, 1 and n 01 (r) = 2 Ψ 0 (r, r 2 )Ψ 1 (r, r 2 )d 3 r 2 , is exactly reproduced by the non-interacting KS electrons.…”

“…To find the exact xc potential, we will need to invert the time-dependent KS equation for the threedimensional case, but first we need to find the exact densities of the interacting eigenstates and the transition density in order to construct the target density Eq. (11).…”

“…While perturbations around the ground-state yields a formalism for excited states, their couplings, and response, it is particularly the generality and practical efficiency of the real-time formulation that has led to the possibility of applications on large systems which could not be done otherwise, e.g. [5][6][7][8][9][10][11][12][13][14][15][16][17][18].…”

Unexpected dipole instabilities in small molecules after ultrafast XUV irradiation

“…Closer inspection of the evolving dipole on a logarithmic scale (not shown) reveals that the envelope of the dipole signal up to 8 fs increases exponentially, as is typical for an instability. In order not to be fooled by artifacts, we have scrutinized our numerical treatment by varying numerical parameters and by performing control calculations using two other full 3D computer packages (EDAMAME [43] and QDD [36]). The effect persists.…”