Charge transfer, double and bond-breaking excitations with time-dependent density matrix functional theory

Time-dependent density functional theory (TDDFT) in its current adiabatic implementations exhibits three remarkable failures: (a) completely wrong behavior of the excited state surface along a bond-breaking coordinate; (b) lack of doubly excited configurations; (c) much too low charge transfer excitation energies. These TDDFT failure cases are all strikingly exhibited by prototype two-electron systems such as dissociating H2 and HeH+. We find for these systems with time-dependent density matrix functional theory that: (a) Within previously formulated simple adiabatic approximations, the bonding-to- antibonding excited state surface as well as charge transfer excitations are described without problems, but not the double excitations; (b) An adiabatic approximation is formulated in which also the double excitations are fully accounted for. © 2008 The American Physical Society

Molecular exchange-correlation Kohn-Sham potential and energy density from ab initio first- and second-order density matrices: examples for XH (X=Li, B,F).

The molecular Kohn–Sham exchange‐correlation potential vxc and the energy density εxc have been constructed from ab initio first‐ and second‐order density matrices for the series XH (X=Li, B, F). The way various effects of electronic structure and electron correlation manifest themselves in the shape of vxc and εxc has been analyzed by their decomposition into various components; the potential of the exchange‐correlation hole, the kinetic component and (in the case of vxc) the ‘‘response’’ component. The kinetic energy of noninteracting particles Ts, the kinetic part of the exchange‐correlation energy Tc, and the energy of the highest occupied molecular orbital εN have been obtained with reasonable accuracy and the effect of bond formation on these functionals has been studied

Spin Resolution of the Electron-Gas Correlation Energy: Positive same-spin contribution

The negative correlation energy per particle of a uniform electron gas of density parameter $r_s$ and spin polarization $\zeta$ is well known, but its spin resolution into up-down, up-up, and down-down contributions is not. Widely-used estimates are incorrect, and hamper the development of reliable density functionals and pair distribution functions. For the spin resolution, we present interpolations between high- and low-density limits that agree with available Quantum Monte Carlo data. In the low-density limit for $\zeta = 0$, we find that the same-spin correlation energy is unexpectedly positive, and we explain why. We also estimate the up and down contributions to the kinetic energy of correlation.Comment: new version, to appear in PRB Rapid Communicatio

The spin-unrestricted molecular Kohn-Sham solution and the analogue of Koopmans's theorem for open-shell molecules

The construction of Kohn-Sham (KS) solution from ab initio spin densities is described for prototype doublet molecules such as N

Double excitation effect in non-adiabatic time-dependent density functional theory with an analytic construction of the exchange-correlation kernel in the common energy denominator approximation

Time-dependent density functional (response) theory (TDDF(R)T) is applied almost exclusively in its adiabatic approximation (ATDDFT), which is restricted to predominantly single electronic excitations and neglects additional roots of the TDDFT eigenvalue problem stemming from the interaction between single and double excitations. We incorporate the effect of the latter interaction into a non-adiabatic frequency-dependent and spatially non-local Hartree-exchange- correlation (Hxc) kernel fCEDAHxc (

Asymptotic correction of the exchange-correlation kernel of time-dependent density functional theory for long-range charge-transfer excitations

The systematic underestimation of excitation energy