We have calculated the lowest excitation energies and the static dipole polarizability of Li-as well as the electron affinity of Li using current quantum-chemical methods, including full CI. We have studied the convergence of the polarizability with the size of the orbital basis set. We find that electron correlation has a dramatic effect on the polarizability reducing it to roughly half its SCF value. MBPT calculations through fourth-order and perturbative propagator methods give an unsatisfactory description of the electron correlation whereas polarization propagator methods based on a coupled-cluster reference state give a polarizability in fair agreement with the full CI result. © 1988.
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