Simple remedy for spurious states in discrete k(dot)p models of   semiconductor structures
  The spurious states found in numerical implementations of envelope function models for semiconductor heterostructures and nanostructures are artifacts of the use of the centered-difference formula. They are readily removed by employing a first-order difference scheme. The technique produces none of the loss of accuracy that is commonly feared from lower-order formulations; the fidelity to the continuum band structure is actually improved. Moreover the stability is absolute, thus no adjustments to the model parameters are required. These properties are demonstrated in an explicit calculation of a 3-band model of a semiconductor superlattice. 
William R. Frensley and Raja N. Mir
cond-mat.mes-hall