A hybrid functional for the exchange-correlation kernel in   time-dependent density functional theory
  A review of the approximations in any time-dependent density functional calculation of excitation energies is given. The single-pole approximation for the susceptibility is used to understand errors in popular approximations for the exchange-correlation kernel. A new hybrid of exact exchange and adiabatic local density approximation is proposed and tested on the He and Be atoms. 
Kieron Burke, Martin Petersilka, and E.K.U. Gross