Atomic Arrangement in Vitreous Selenium

摘要: X-ray diffraction data at 25 and - 196\ifmmode^\circ\else\textdegree\fi{}C have been used to obtain radial distribution functions for amorphous hexagonal selenium. The selenium exhibited strong correlation peaks 2.34, 3.75, 5.8, 7.2, 9.3 \AA{}, with minor 4.3, 4.7, 5.1, 7.7, 10.0, 10.5 \AA{}. first two distances are observed in both the form, which consists of spiral chains, monoclinic forms, consist eight-membered puckered rings. remaining major do not correspond intramolecular any crystalline forms. Attempts were made match experimental function models involved perturbations atom positions A computer array consisting 100 was used, chosen by a Monte Carlo procedure allowed only those improved fit function. It shown that relatively small rms static displacements, order 0.20 sufficient convert ring structures vitreous whereas much larger perturbations, 0.7 required chain structure into form would give suitable atomic configurations perturbed consisted mainly slightly distorted There few locations where rings had opened sufficiently so atoms vicinity opening appeared nearest-neighbor trigonal symmetry rather than ring. optical Raman spectra provide evidence presence ${\mathrm{Se}}_{8}$ weaker indication near-neighbor symmetry. We conclude rings, along an occasional is develop weak localized or greatly deformed chains.