2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/17168We have found the equations that determine the self-adjoint extensions, and thus the boundary conditions, of the differential operator used in the multi-band k.p-theory, when the coefficients in the Kane-matrix are piecewise constant. Both the one-dimensional and the three-dimensional case have been investigated. A numerical calculation shows that the choice of boundary conditions affects the energy eigenvalues for a quantum well.13 pages, 2 figuresMaterials Sciencetext