Asymmetries of local arsenic bonding sites inAsxS1−xandAsxSe1−xglasses

Abstract

We simulate high-field ${}^{75}\mathrm{As}$ NMR line shapes by numerically diagonalizing the full Hamiltonian in the laboratory frame. The results of high field ${}^{75}\mathrm{As}$ NMR in both glassy and polycrystalline ${\mathrm{As}}_{x}{\mathrm{S}}_{1\ensuremath{-}x}$ and ${\mathrm{As}}_{x}{\mathrm{Se}}_{1\ensuremath{-}x}$ binary systems are analyzed using this more accurate line-shape simulation. We find that for $x=0.4$ the asymmetry parameters of the electric-field gradient at As sites are less than 0.2 in both glassy and the polycrystalline samples, revealing the similarity of the local order in these two materials. In the glasses, we also find evidence of the influence of statistical fluctuations on the various bonding configurations, even at the stoichiometric concentrations.