Angle-resolved photoemission theory for valence electrons. I. A calculation scheme by the multi-slice method

A one-step photoemission calculation scheme for valence electrons is presented which uses (to construct the initial- and final-state wavefunctions) the multi-slice technique, which has been developed for low-energy electron diffraction (LEED). Included in the scheme is the possibility of having an over-layer or an arbitrarily shaped surface barrier, and realizing both the electron and hole life-times by means of an imaginary part to the energy. The photoemission intensity due to surface states can also be calculated separately by the same procedure. The advantage of the scheme is that because the crystal potential is divided into arbitrarily thin slices, problems associated with the frequency used muffin-tin potential do not arise.