Time-dependent Hartree-Fock strengths

With ab initio methods there are two distinct approaches to calculating time dependent properties. One is the analytic derivative approach, where explicit expressions are obtained for the derivatives of the dipole moment or of the pseudoenergy. The other approach, known as response theory calculates the response function directly by time dependent perturbation theory. In general finite field methods are not applicable for dynamit properties except that, e.g., j8(ru 0, ru) could be calculated by the finite difference of a ay,a)) calculated at two different field strengths. Consider first methods based on Hartree-Fock theory, known collectively as TDHF. 

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