Amorphous phosphorus: A cluster-network model

We have performed an extensive theoretical investigation of amorphous phosphorus (a-P) using the molecular-dynamics--density-functional method. The energy surfaces and forces for 124 atoms in a constant-volume simple cubic cell were calculated using the density-functional formalism, with a local-density approximation for the exchange-correlation energy. Pair correlation functions g(r), structure factors S(Q), phonon densities of states, ring statistics, and various static distribution functions (including distributions of bond and pyramid angles) were computed and compared with experimental and theoretical data where available. Although amorphous solids are usually likened to crystalline polymorphs with known structures, we find that the structure of rapidly quenched a-P resembles a network of small Pₙ clusters more than any of its common crystalline allotropes.