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Slichter, C.P. Schwartz, Paul Michael 2011-07-13T16:19:58Z 2011-07-13T16:19:58Z 10000-01-01 1969 A theory is presented to explain the behavior of ammonium chloride near the first order phase transition at 240K in terms of· a physical model that has singular and nonsingu1ar parts of the free energy coupled together. The singularity is normally associated with a second order phase transition, but it can lead to a first order transition in the model discussed. The heat capacity at constant pressure is measured in the neighborhood of the transition in order to test the predictiors of the theory. An A.C. technique is used to measure the heat capacity of ammonium chloride single crystals, and a discussion of the experimental factors involved in making the measurement is given. The heat capacities measured showed a strong sample dependence. Values are obtained for parameters occurring in the theory and are compared with those obtained from other experiments on ammonium chloride and from theoretical predictions. In particular, the volume dependence of the interaction responsible for the transition is in qualitative agreement with a prediction based upon an octopo1e-octopo1e, electrostatic interaction. The critical exponents a+ and a are found to be in the neighborhood of .7, which is quite different from. the predictions of Ising model calculations. Submitted by Carolyn Mead (cmead2@illinois.edu) on 2011-07-13T16:19:58Z No. of bitstreams: 1 1969_schwartz.pdf: 2067787 bytes, checksum: 958d822362da93de14acd56a5c598765 (MD5) Made available in DSpace on 2011-07-13T16:19:58Z (GMT). No. of bitstreams: 1 1969_schwartz.pdf: 2067787 bytes, checksum: 958d822362da93de14acd56a5c598765 (MD5) Previous issue date: 1969 Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Carolyn Mead (cmead2@illinois.edu) on 2011-07-13T16:19:58Z Item is restricted indefinitely. Restriction data tranferred 2014-07-01T11:32:55-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: Thesis Thesis U of I Only 6075554 http://hdl.handle.net/2142/25796 en 1969 Paul Michael Schwartz heat capacity ammonium chloride order-disorder transition first order phase transition The heat capacity of ammonium chloride near the order-disorder transition Dissertation / Thesis text Physics Physics University of Illinois at Urbana-Champaign Dissertation Ph.D.