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

Abstract

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 DMol 3 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.