{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/23740"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/23740","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Thermal vacancies in HCP helium-4","abstract":"Activation energies of thermal vacancies have been determined in hcp $\\sp4$He as a function of molar volume. A sensitive strain gauge was used to measure the temperature dependence of the pressure in twenty crystals between 18.17 and 20.9 cm$\\sp3$/mole. Absolute lattice parameters at low temperatures were measured for many of these crystals. The temperature dependence of the relative lattice parameter was measured in selected crystals. This provided lower bounds on the vacancy activation energy.","abstract_html":"Activation energies of thermal vacancies have been determined in hcp $\\sp4$He as a function of molar volume. A sensitive strain gauge was used to measure the temperature dependence of the pressure in twenty crystals between 18.17 and 20.9 cm$\\sp3$/mole. Absolute lattice parameters at low temperatures were measured for many of these crystals. The temperature dependence of the relative lattice parameter was measured in selected crystals. This provided lower bounds on the vacancy activation energy.","abstract_has_math":true,"creators":["Thorpe, John Clifton"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Physics, Condensed Matter","degree_department":null,"school":null,"contributors":["Simmons, R.O."],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2011,"date_issued":"2011-05-07T14:25:19Z","date_published":"2011-05-07T14:25:19Z","updated_at":"2026-07-22T22:25:22Z","subjects":["Physics, Condensed Matter"],"languages":["eng"],"rights":["Copyright 1991 Thorpe, John Clifton"],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["AAI9124500","(UMI)AAI9124500"],"render_values":[{"text":"AAI9124500","href":null,"code":true},{"text":"(UMI)AAI9124500","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/2142/23740","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Simmons, R.O."]},{"key":"dc:creator","label":"Author","values":["Thorpe, John Clifton"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2011-05-07T14:25:19Z","10000-01-01","1991"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Physics, Condensed Matter"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph.D."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Physics, Condensed Matter"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 1991 Thorpe, John Clifton"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["AAI9124500","(UMI)AAI9124500","http://hdl.handle.net/2142/23740"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Activation energies of thermal vacancies have been determined in hcp $\\sp4$He as a function of molar volume. A sensitive strain gauge was used to measure the temperature dependence of the pressure in twenty crystals between 18.17 and 20.9 cm$\\sp3$/mole. Absolute lattice parameters at low temperatures were measured for many of these crystals. The temperature dependence of the relative lattice parameter was measured in selected crystals. This provided lower bounds on the vacancy activation energy.","The activation energies determined here agree at all reported molar volumes with those from previous measurements of pressure in hcp $\\sp4$He. The lower bounds on the activation energies from the relative lattice parameter measurements are consistent with those determined from the pressure. Below 20 cm$\\sp3$/mole the activation energies reported here are in disagreement with those from ion mobility, NMR, and plastic deformation experiments. The determination of vacancy activation energies from the measured pressure requires knowledge of the phonon pressure. Difficulties with the present understanding of the phonon pressure are discussed.","Made available in DSpace on 2011-05-07T14:25:19Z (GMT). No. of bitstreams: 2 license.txt: 4922 bytes, checksum: 910b249b4beec47e7ab768910c8f966f (MD5) 9124500.pdf: 5502854 bytes, checksum: b1fb5958d00316f576197e07092f93f8 (MD5) Previous issue date: 1991","Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Howard Ding (hding2@illinois.edu) on 2011-05-07T15:06:31Z Item is restricted indefinitely.","Restriction data tranferred 2014-07-01T11:31:57-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: ETDs are only available to UIUC Users without author permission","ETDs are only available to UIUC Users without author permission","U of I Only"]},{"key":"dc:title","label":"Title","values":["Thermal vacancies in HCP helium-4"]}]}],"canonical_facts":{"dc:contributor":["Simmons, R.O."],"dc:creator":["Thorpe, John Clifton"],"dc:date":["2011-05-07T14:25:19Z","10000-01-01","1991"],"dc:description":["Activation energies of thermal vacancies have been determined in hcp $\\sp4$He as a function of molar volume. A sensitive strain gauge was used to measure the temperature dependence of the pressure in twenty crystals between 18.17 and 20.9 cm$\\sp3$/mole. Absolute lattice parameters at low temperatures were measured for many of these crystals. The temperature dependence of the relative lattice parameter was measured in selected crystals. This provided lower bounds on the vacancy activation energy.","The activation energies determined here agree at all reported molar volumes with those from previous measurements of pressure in hcp $\\sp4$He. The lower bounds on the activation energies from the relative lattice parameter measurements are consistent with those determined from the pressure. Below 20 cm$\\sp3$/mole the activation energies reported here are in disagreement with those from ion mobility, NMR, and plastic deformation experiments. The determination of vacancy activation energies from the measured pressure requires knowledge of the phonon pressure. Difficulties with the present understanding of the phonon pressure are discussed.","Made available in DSpace on 2011-05-07T14:25:19Z (GMT). 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