We have calculated the value of the shear-deformation-potential constant ${\mathrm{\Xi }}_{\mathit{u}}$ of the conduction-band minima of Si and its temperature coefficient d${\mathrm{\Xi }}_{\mathit{u}}$/dT. The value of ${\mathrm{\Xi }}_{\mathit{u}}$ is 9.0 eV for an ab initio pseudopotential calculation and 10.8 eV by the empirical-pseudopotential method (EPM), in good agreement with our experiment. The EPM calculations of the temperature dependence of ${\mathrm{\Xi }}_{\mathit{u}}$ yield the values of (d${\mathrm{\Xi }}_{\mathit{u}}$/dT)${\mathrm{\Vert }}_{\mathrm{DW}}$=-0.04 meV/K due to the Debye-Waller contribution, and (d${\mathrm{\Xi }}_{\mathit{u}}$/dT)${\mathrm{\Vert }}_{\mathrm{TE}}$=-0.04 meV/K for thermal expansion. We suspect and suggest that the existing experimental value of d${\mathrm{\Xi }}_{\mathit{u}}$/dT≃+3 meV/K is unreliable due to large experimental uncertainty.

• Received 25 May 1990

DOI:https://doi.org/10.1103/PhysRevB.42.5714