A comparative study of the atomic structures of Ge-doped As4S3 and P4Se3 molecular glasses

The structures of pseudo-binary P-Se and As-S glasses with compositions close to the P4Se3 and As4S3 stoichiometry with a few atom %Ge doping were determined using Monte Carlo simulations constrained by density and x-ray scattering measurements. We find that these glasses consist predominantly of P4Se3 and As4S3 molecules. The Ge doping results in some important differences between the two glasses. The P-Se glass displays significantly higher intermolecular connectivity via P-Se-Ge linkages, consistent with the significantly higher glass transition temperature and lower fragility of this liquid compared to its As-S counterpart. We also speculate that a consequence of this difference in the intermolecular connectivity would be to delay any pressure induced conversion from a molecular to a network structure for the Ge doped P-Se glass compared to the Ge-doped As-S glass.