2026-09-21T04:31:32Z https://www.ideals.illinois.edu/oai-pmh

oai:www.ideals.illinois.edu:2142/25801 2023-07-10 col_2142_8859 col_2142_5131 com_2142_8858 com_2142_234 com_2142_5130

Slichter, C.P. Fredericks, George Ernest 2011-07-13T19:23:14Z 2011-07-13T19:23:14Z 10000-01-01 1969 A theory is presented to explain the behavior of the volume of ammonium chloride near the first order transition at 242°K. This theory is able to account for a first order transition by considering the coupling between an elastic lattice system and the order-disorder system. The lattice system gives rise to non-singular terms in the Helmholz Free Energy of the total system. The order-disorder system gives rise to a singular term in the free energy. The coupling of the two subsystems then produces the possibility of the first order transition. The thermal expansion at constant pressure of ammonium chloride was measured in order to test the predictions of the theory. A three terminal bridge measurement of an electrical capacitance determined by the length of single crystals of ammonium chloride was used to measure the thermal expansion of ammonium chloride. A discussion of the experimental arrangement is given. The measured thermal expansion showed sample dependence. Fits of the theory to the data are presented. These fits show qualitative agreement between theory and experiment, but systematic deviations outside the experimental scatter were found, especially near the transition. Values of the critical exponents alpha+ and alpha- range from about .80 to .97, This is in striking disagreement with theoretical calculations using the Ising model. Submitted by Carolyn Mead (cmead2@illinois.edu) on 2011-07-13T19:23:14Z No. of bitstreams: 1 1969_fredericks.pdf: 1706570 bytes, checksum: f39fd6f431249a2abf7cd7ebd5de974f (MD5) Made available in DSpace on 2011-07-13T19:23:14Z (GMT). No. of bitstreams: 1 1969_fredericks.pdf: 1706570 bytes, checksum: f39fd6f431249a2abf7cd7ebd5de974f (MD5) Previous issue date: 1969 Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Carolyn Mead (cmead2@illinois.edu) on 2011-07-13T19:23:14Z Item is restricted indefinitely. Restriction data tranferred 2014-07-01T11:32:51-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: Thesis Thesis U of I Only 6072766 http://hdl.handle.net/2142/25801 en 1969_George Ernest Fredericks thermal expansion ammonium chloride order-disorder transition first order transition elastic lattice system The thermal expansion of ammonium chloride near the order-disorder transition Dissertation / Thesis text Physics Physics University of Illinois at Urbana-Champaign Dissertation Ph.D.