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Title:Equilibrium vacancy concentration measurements and thermal properties of solid krypton
Author(s):Losee, David Lawrence
Doctoral Committee Chair(s):Simmons, R.O.
Department / Program:Physics
Subject(s):equilibrium vacancy
thermal properties
solid krypton
x-ray lattice parameter expansion
rigid-tail cryostat
Abstract:Simultaneous length and x-ray lattice parameter expansion measurements have been made on three 6 mm diam cylindrical specimens of 99.995% purity krypton. The specimens were prepared and held unconstrained in a rigid-tail cryostat in which specimen temperatures could be precisely controlled. The data show a divergence between the bulk and lattice expansions at the higher temperatures which indicates an appreciable concentration of thermally generated defects o at temperatures above 75 K. The equilibrium atomic vacancy concentration inferred from these measurements appears to be represented by n = exp[(2.0 ± 0.5) - (895 ± 1000K)/T]. The monovacancy formation enthalpy and entropy is discussed and compared with other existing theoretical and experimental information on argon and krypton. It appears that the enthalpy of formation for the monovacancy in krypton may not be entirely accounted for by two-body central-force interactions. However, existing calculations of the contribution of threebody interactions to the binding energy of the noble gas solids appear to be of the correct order of magnitude and sign to produce agreement between theory and experiment for the vacancy. Recent measurements of specific heat, isothermal compressibility, and the present thermal expansivity data, allow compilation and analysis of a number of thermodynamic functions of solid krypton. The measurable formation of atomic vacancies at temperatures above 7S oK is seen to make significant contribution to all of the thermal properties of krypton at the higher temperatures. In the lower temperature region, the temperature dependence of the equivalent Debye temperatures for the entropy and for the specific heat, referred to the volume at TOoK, are examined. Moments of the quasiharmonic phonon frequency spectrum are deduced as well as the leading anharmonic coefficient in the free energy. The need for additional precise experimental information at temperatures near the triple point of krypton is stressed. An empirical law of corresponding states is found to describe several properties of the heavy noble gas solids. Estimates of the previously unknown activation energy for self-diffusion in krypton and energies of formation for atomic vacancies in argon and xenon are possible.
Issue Date:1967
Genre:Dissertation / Thesis
Rights Information:1967 David Lawrence Losee
Date Available in IDEALS:2011-07-07
Identifier in Online Catalog:6086873

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