Phonon-dispersion curves, lattice mode Grüneisen parameters, and the coefficients of thermal expansion are calculated for Si and C within a tight-binding model. The results are in good agreement with experimental data. The origin of the negative thermal expansion in Si is examined, and we find that the different thermal-expansion behaviors between Si and C can be explained by the different relative strengths of bond-bending and bond-stretching forces.

• Received 24 September 1990

DOI:https://doi.org/10.1103/PhysRevB.43.5024