Ab initio analytical molecular gradients and Hessians

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Abstract
Molecular gradients and Hessians have been derived for MCSCF, CI, coupled cluster, and Mo/ller–Plesset wave functions. In deriving the gradients and Hessians, atomic orbital basis set effects have been incorporated into the finite basis Hamiltonian, and unitary exponential operators have been used to determine the wave function’s configuration and orbital responses. The gradients and Hessians are expressed in terms of products of configuration and orbital responses and matrices of the same form as the gradient and Hessian matrices appearing in energy and wave function optimizations. The molecular gradients and Hessians have also been cast into forms that are computationally very tractable.