0000000000702056
AUTHOR
Thuat T. Trinh
Thermodynamic Characterization Of Two Layers Of CO2 On A Graphite Surface
We find by examination of density profiles that carbon dioxide adsorbs on graphite in two distinct layers. We report the activity coefficient, entropy and enthalpy for CO2 in each layer using a convenient computational method, the Small System Method, thereby extending this method to surfaces. This opens up the possibility to study thermodynamic properties for a wide range of surface phenomena. © 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).
Calculation of the chemical potential and the activity coefficient of two layers of CO2 adsorbed on a graphite surface.
We study the adsorption of carbon dioxide at a graphite surface using the new Small System Method, and find that for the temperature range between 300 K and 550 K most relevant for CO2 separation; adsorption takes place in two distinct thermodynamic layers defined according to Gibbs. We calculate the chemical potential and the activity coefficient of both layers directly from the simulations. Based on thermodynamic relations, the entropy and enthalpy of the CO2 adsorbed layers are also obtained. Their values indicate that there is a trade-off between entropy and enthalpy when a molecule chooses for one of the two layers. The first layer is a densely packed monolayer of relatively constant e…
Bridging scales with thermodynamics: from nano to macro
We have recently developed a method to calculate thermodynamic properties of macroscopic systems by extrapolating properties of systems of molecular dimensions. Appropriate scaling laws for small systems were derived using the method for small systems thermodynamics of Hill, considering surface and nook energies in small systems of varying sizes. Given certain conditions, Hill's method provides the same systematic basis for small systems as conventional thermodynamics does for large systems. We show how the method can be used to compute thermodynamic data for the macroscopic limit from knowledge of fluctuations in the small system. The rapid and precise method offers an alternative to curre…