Plasma energies forA−15compounds

Recent infrared studies by Yao and Schnatterly on ${\mathrm{V}}_3$Si and ${\mathrm{Nb}}_3$Ge films have determined the optical parameters for these materials, including the Drude plasma energy ${\Omega }_p$. It is shown that a tight-binding energy-band model, based on augmented-plane-wave and self-consistent pseudopotential calculations, yields plasma energies ${\Omega }_p$ that are within 20%-25% of these observed values. It is suggested that ${\Omega }_p$ provides a useful criterion for evaluating the gross features of any band model for the $A-15$ compounds, especially since it is relatively insensitive to details such as fine structure in the density of states.