Structural properties of amorphous selenium: An ab initio molecular-dynamics simulation

We use a new approach to generate amorphous selenium structures by an ab initio molecular dynamics method. We start with crystalline cubic supercells in a diamond-like structure with 64, 150 and 216 atoms, and with the experimental microscopic densities of ρ = 0.0324 (4.25 g cm−3) and ρ = 0.0340 atoms Å−3 (4.45 g cm−3). The samples are amorphized using DMol3 from the suite in Material Studio 3.2® by heating the periodic structures to just below the melting point (the undermelt-quench approach) and then cooling them down to 0 K. The structures are relaxed by annealing and quenching, and finally a geometry optimization is carried out. We report radial distribution functions g(r), bond angle distributions and dihedral angle distributions. We find that the amorphous structure, for both densities, is mainly formed by chains but not at all linear, there are some ring-like structure although not closed. Also the Radial Distributions Functions, RDFs, of Se have maxima at 2.35 Å and 3.75 Å for the first and second neighbors, respectively.