Electronic Structure of Amorphous Ge

The electronic spectrum of amorphous Ge is examined in view of the recent Letter of Brust. Using Brust's calculations, it is shown that even a partial retention of $\overrightarrow{\mathrm{k}}$ as a quantum number results in prediction of a strong modulation in photoemission energy-distribution curves. Such moducation is not found experimentally. It is concluded that there is no evidence that $\overrightarrow{\mathrm{k}}$ is a meaningful quantum number in this amorphous material and that the density of states of the amorphous and the crystalline materials differ quite significantly. It is pointed out that Brust's model should be particularly useful in examining the amorphous-to-crystalline transformation.