Time-dependent multiconfigurational Hartree–Fock theory

Abstract

A time dependent version of multiconfigurational Hartree–Fock theory is formulated as an extension of the time-dependent Hartree–Fock approximation. The time variation of the reference state is calculated using a form of Frenkel’s variation principle, which was suggested by Langhoff, Epstein, and Karplus. A linearized form of the equations provides linear response functions, which transform correctly under contact transformations generated by one particle operators. A consequence of this feature is that the various formally equivalent expressions for the oscillator strengths of electronic transitions will give the same result, apart from truncation errors when a finite orbital basis is used. Example calculations are carried out for some π electron systems within the Pariser–Parr–Pople model using a correlated reference state suggested by Clementi and Veillard.