X-ray diffraction study of compressed solid argon and krypton

Abstract

New methods were developed and applied both to obtain very precise x-ray lattice parameters along the melting curves of solid argon and solid krypton and to measure changes in vacancy concentrations along quasi-isochores for both these substances. The uncertainty of the lattice parameters obtained along melting was estimated to be 27 ppM. These measurements are believed to be the most precise melting line density data ever reported for argon and krypton. The uncertainty of expansion measurements off melting was estimated to be 7 ppM, and this implies a sensitivity of these data of 2.1 x 10-5</ to changes in the concentration of vacancies. Five separate argon crystals yielded lattice parameters along the argon melting curve over the temperature range 86.7 K to 124.3 K. This corresponded to the molar volume range 23.43 cm3<//mole to 24.54 cm3<//mole. Vacancy information was obtained from three of these crystals. A krypton crystal yielded melting curve lattice parameters over the temperature range 127.3 K to 138.9 K which corresponded to the molar volume range 29.32 cm3<//mole to 29.62 cm3<//mole. These constitute the first reported melting densities for solid krypton in the range given. The krypton crystal also yielded vacancy information. The temperature region just belowmore » melting was investigated in some detail for one argon crystal and the krypton crystal, and an anomalously rapid variation in lattice parameter within a degree or so of melting was observed in both.« less Authors: Macrander, Albert Tiemen Publication Date:1977-01-01 OSTI Identifier:5346139 Report Number(s):COO--1198-1186 DOE Contract Number:EY-76-C-02-1198 Resource Type:Thesis/Dissertation Resource Relation:Other Information: Thesis Research Org:Illinois Univ., Urbana, IL (United States) Sponsoring Org:USDOE Country of Publication:United States Language:English Subject: 36 MATERIALS SCIENCE; ARGON; MELTING POINTS; KRYPTON; HIGH PRESSURE; LATTICE PARAMETERS; MEDIUM TEMPERATURE; SOLIDS; VACANCIES; VERY HIGH PRESSURE; CRYSTAL DEFECTS; CRYSTAL STRUCTURE; ELEMENTS; NONMETALS; PHYSICAL PROPERTIES; POINT DEFECTS; RARE GASES; THERMODYNAMIC PROPERTIES; TRANSITION TEMPERATURE 360603* -- Materials-- Properties; 360602 -- Other Materials-- Structure & Phase Studies