Ab initio calculations of the excitonic spectra of the alkali iodides including relativistic effects

We extend our previous studies of local excitons in the alkali halides to include relativistic effects such as spin-orbit, mass-velocity, and Darwin corrections. We examine the alkali iodide series and certain features in the optical absorption spectra which are due to local excitons. We find that we must include relativistic effects, as well as an appropriate number of neighboring-ion shells, if we are to compute the excitonic energies accurately. © 1987 The American Physical Society

Perturbation-theory method of calculating the energies and excitation energies of atomic, molecular, and solid-state systems

We investigate a general, approximate method for solving the many-electron Schrödinger equation for a molecule or a molecular fragment representing a solid. The method chosen is the unrestricted Hartree-Fock method augmented by a size-consistent many-body perturbation-theory correction. For simplicity, a single-reference development is presented. The extension to multireference formalisms is straightforward if tedious. A few sample results are obtained to illustrate the potential of the method. © 1986 The American Physical Society