Relativistic corrections to the electronic states of heavy atomic crystals are investigated by solving the Dirac equation for the Kronig-Penney potential, subject to certain boundary conditions, which differ from those used in earlier studies. These new boundary conditions enable the mathematics to be simplified considerably, without obscuring any of the relativistic effects found previously. Comparisons are made between the results obtained using the different sets of boundary conditions.

• Received 8 September 1969

DOI:https://doi.org/10.1103/PhysRevB.1.1858