Difficulties in application of the orthogonalized plane wave method of determining energy levels in solids may arise under two conditions: If (1) the potential around an atom in the crystal is appreciably different from that of a free atom; or if (2) the wave function for a valence electron state is orthogonal by reasons of symmetry to all core states. Ways of treating these problems are discussed, and applied to two eigenvalues in iron.

• Received 11 October 1954

DOI:https://doi.org/10.1103/PhysRev.97.933