Pentane Adsorbed on MgO(100) Surfaces: A Thermodynamic, Neutron, and Modeling Study

DOI: 10.1021/jp509129d

Authors: Richard E. Cook (Department of Chemistry, University of Tennessee) , Tom Arnold (Diamond Light Source) , Nicholas Strange (Department of Chemistry, University of Tennessee) , Mark Telling (Rutherford Appleton Laboratory, ISIS Spallation Neutron Source) , John Larese (University of Tennessee)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: The Journal Of Physical Chemistry C , VOL 119 (1)

State: Published (Approved)
Published: December 2014

Abstract: Thermodynamic measurements using high-resolution volumetric adsorption isotherms were performed on n-pentane films physisorbed on MgO(100) surfaces between 181 K and 244 K. The isotherms show two distinct adsorption steps before the saturated vapor pressure is reached. The heat of adsorption is found to be 33.7 ± 0.3 kJ mol–1 for the first layer and 32.9 ± 0.3 kJ mol–1 for the second layer. Evolution of the two-dimensional compressibility, as a function of temperature, suggests that a phase transition occurs at 185.5 ± 1 K in the second layer. Neutron diffraction is used to establish that the melting of the pentane monolayer takes place between 101 K and 105 K. Computer modeling studies indicate that the pentane molecules adsorb with the molecular axis parallel to the substrate plane. These results suggest that the monolayer forms a solid with a rectangular unit cell, consistent with the neutron diffraction measurements.

Subject Areas: Chemistry, Physics, Materials


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