Statistical average of model orbital potentials for extended systems: Calculation of the optical absorption spectrum of liquid water

Time-dependent density functional theory (TD-DFT) calculations of the electronic response of molecular and bulk liquid water based on a very accurate orbital-dependent ground-state exchange-correlation potential, the statistical average of (model) orbital potentials (SAOP), and on the adiabatic local density approximation (ALDA) for the exchange-correlation kernel are described. The quality of the calculated excitation energies, both in the molecule and in the liquid, is assessed by comparison to hybrid TD-DFT calculations and experimental data. A combination of classical molecular dynamics simulations and TD-DFT calculations sampling several disordered configurations of a small liquid sample is then used to simulate the optical absorption spectrum in the region of 0-15 eV. The resulting room-temperature absorption profile is discussed in connection with previous TD-DFT calculations as well as with results from Green's function theory and experiment. (C) 2010 American Institute of Physics. [doi:10.1063/1.3414351]