A theoretical analysis of interstitial hydrogen : pressure-composition-temperature, chemical potential, enthalpy and entropy
Author(s)Orondo, Peter Omondi
Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science.
Peter L. Hagelstein.
MetadataShow full item record
We provide a first principles analysis of the physics and thermodynamics of interstitial hydrogen in metal. By utilizing recent advances in Density Functional Theory (DFT) to get state energies of the metal-hydrogen system, we are able to model the absorption process fairly accurately. A connection to experiment is made via Pressure-Composition-Temperature (PCT) isotherms, and thermodynamic molar quantities. In the model, we understand the excess entropy of absorbed hydrogen in terms of the change in its accessible microstates. A connection is also made between the entropy and electronic states of interstitial hydrogen. However, our model indicates that this connection is too small to account for experimental results. Therefore, a conclusion is made that the entropy of absorbed hydrogen is mostly (non-ideal) configurational in nature. To model the latter in a manner consistent with experiment, we have explored a new model that posits a weak binding between clusters of hydrogen atoms at neighboring sites. We have developed a formulation and fitted the results to experimental data. We find a least squares fitting of the model to the entropy and enthalpy results in model parameters which seem physically reasonable. The resulting model appears to provide a natural physical explanation for the dependence of the excess entropy on loading.
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 371-373).
DepartmentMassachusetts Institute of Technology. Department of Electrical Engineering and Computer Science.
Massachusetts Institute of Technology
Electrical Engineering and Computer Science.