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Heat capacity of multilayer methane on graphite: Phase transitions in the first four layers

Lysek, M. J. and LaMadrid, M. A. and Day, P. K. and Goodstein, D. L. (1993) Heat capacity of multilayer methane on graphite: Phase transitions in the first four layers. Physical Review B, 47 (12). pp. 7389-7400. ISSN 1098-0121. http://resolver.caltech.edu/CaltechAUTHORS:LYSprb93

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Abstract

We present high-resolution heat-capacity data for methane adsorbed on graphite for nominal coverages of 0.87 to 7 layers, from T = 70 to 120 K. For films thicker than 1.1 layers, we find capillary condensate coexisting with the film. We have performed heat-capacity scans on films formed by both adsorption and desorption. By comparing the locations of the phase transitions in the chemical potential mu vs T plane, we find that there is no significant interaction between the film and the capillary condensate. The heat-capacity signals from the films map out an unexpectedly rich set of phenomena for the second, third, and fourth layers, including a two-dimensional triple point and a liquid-gas coexistence region for each layer. The fourth-layer critical temperature we find is lower than previous values found by vapor-pressure isotherms.


Item Type:Article
Additional Information:©1993 The American Physical Society. Received 21 September 1992. The authors would like to acknowledge many useful conversations with Professor P. Weichman, Professor M. Cross, Professor J. M. Phillips, Professor G. B. Hess, and Professor J. Larese. M. A. L. acknowledges support from the Continental Oil Fund. This work was supported by DOE Grant No. DE-FG03-85ER45192.
Subject Keywords:ARGON FILMS; NEUTRON-DIFFRACTION; TRIPLE-POINT; ADSORPTION; BEHAVIOR; FACE; AR; XE
Record Number:CaltechAUTHORS:LYSprb93
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:LYSprb93
Alternative URL:http://dx.doi.org/10.1103/PhysRevB.47.7389
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:3168
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:18 May 2006
Last Modified:26 Dec 2012 08:52

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