Unit cell parameters of 32S8 – 34S8 solid mixtures and their extremal behavior

• Published in: The Journal of physics and chemistry of solids Vol. 139; p. 109316
• Main Authors: Sukhanov, Maksim V., Velmuzhov, Aleksandr P., Kotereva, Tatyana V., Churbanov, Mikhail F., Knyazev, Aleksandr V., Dmitrienko, Anton S.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.04.2020
• Subjects: Extremal behavior; Isotope ordering; Lattice parameters; Molecular adduct; Solid solution; Sulfur isotopes; Sulfur isotopes; Extremal behavior; Lattice parameters; Solid solution; Molecular adduct; Isotope ordering
• ISSN: 0022-3697; 1879-2553
• DOI: 10.1016/j.jpcs.2019.109316

The behavior of isotopic mixtures of polyatomic molecular compounds can have a critical character. Orthorhombic sulfur α-S8 is a typical representative of polyatomic molecular compounds among simple substances. Samples comprised of orthorhombic sulfur of different 32S and 34S ratio have been prepared and examined with powder X-Ray diffractometry in the temperature region from −100 to +90 °С. Unit cell parameters of sulfur samples with intermolecular isotopic substitution, containing 0.4 to 0.5 parts of 34S8 molecules, differ radically from the samples of the isotopic composition close to pure α-32S8 and α-34S8. Maximal deviation of unit cell volume −0.17% at −100.0 °C is observed for the sample with a part of 34S8 molecules being 0.45. Such a behavior could well be attributed to the ordering between 32S8 and 34S8 molecules in the crystal that can be triggered by lowering temperature. •Inter- and intramolecular isotope substituted compounds of sulfur were obtained.•Unit cell parameters of α-32S8, α-34S8 and mixtures with 25 and 75 mol.% 34S8 are not different.•Unit cell parameters of mixtures with 40–50 mol.% 34S8 demonstrate extremal contraction.•Ordering of monoisotopic molecules S8 in the mixed crystal.