Density-matrix representation of nonadiabatic couplings in time-dependent density functional (TDDFT) theories

Closed expressions for nonadiabatic coupling between the ground and an excited electronic state of a molecule are derived by representing the time-dependent density functional (TDDFT) equations in a form of classical dynamics for the Kohn-Sham (KS) single-electron density matrix. Applicability of Krylov-space-type fast algorithms to nonadiabatic TDDFT as well as the representivity of the time-dependent charge density of a driven system are discussed. (C) 2000 American Institute of Physics. [S0021-9606(00)01608-1].