Time-evolution of multiconfiguration density functions driven by nuclear motions

Abstract

Chemical bonding in nonstationary states is treated within a multiconfiguration time-dependent Hartree-Fock (MCTDHF) approach, combined with an eikonal description of the nuclear motions valid for several degrees of freedom. The treatment focuses on the use of density matrices, insofar as these have an appealing physical meaning and lead to linear equations for the electron dynamics. The time-dependent variational principle is used with a trial wave function in an eikonal representation to derive equations for its phase and preexponential factor, with the latter constructed from an MCTDHF expansion. The equations for configuration coefficients and for the molecular spin orbitals are derived, and the equations are rewritten in a compact form, for density matrices, suitable for numerical work. A solution of the coupled equations is given within an expansion around relaxing density matrices. This provides a computational procedure suitable for coupling of the slow nuclear variables with the fast density matrix elements for configurations and molecular orbitals. © 1996 John Wiley & Sons, Inc.