The energy-band structure of SnTe is calculated using the augmented-plane-wave method, taking into account the relativistic corrections. The resulting wave functions at $L$ are used to calculate momentum matrix elements. These matrix elements are then used in a k·p perturbation calculation in the presence of a magnetic field to obtain band parameters at point $L$ in the Brillouin zone. Nonparabolic expansions for the conduction and valence bands at $L$ are obtained using Cohen's model. The effect of strain on the energy levels at $L$ is calculated using the deformation-potential theory. The results indicate a complicated shape for the valence band at $L$, with two maxima at each side of $L$ on the face of the Brillouin zone. A record set of apparent maxima is found in the $\Sigma$ direction at $\mathbf{k}=\left(\frac{\pi }{a}\right)(\frac{4}{5},\frac{4}{5},0)$. This is consistent with the "two-valence-band" model suggested to explain the experimental results. We are investigating the possibility that these extrema may be saddle points. The conduction- and valence-band-edge symmetries at $L$ are opposite to those of the lead chalcogenides, as are the band-gap deformation potentials at this point (-8.68 eV for SnTe and 11.55-17.24 eV for the others). This is in agreement with the experimentally proposed "band-inversion" model.

• Received 23 December 1968

DOI:https://doi.org/10.1103/PhysRev.182.821