We present detailed calculations using the total energy pseudopotential method of relaxed amorphous structures at various densities formed metastably in silicon and carbon. These calculations show a number of interesting features: fivefold coordination of atoms in silicon but not in carbon, bond lengths in carbon increased at reduced volume, with the opposite trend in silicon, and three-center orbitals in carbon. Also, the energy is nearly independent of volume in carbon, suggesting that properties of amorphous carbon will depend strongly on the growth process.

• Received 13 January 1997

DOI:https://doi.org/10.1103/PhysRevB.55.14059