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Comparing B3LYP and its dispersion-corrected form to B97-D3 for studying adsorption and vibrational spectra in nitrogen reduction

Grossman, Esther Florence
http://rave.ohiolink.edu/etdc/view?acc_num=ouhonors155628790845

Abstract Details

2019, Bachelor of Science (BS), Ohio University, Engineering Physics.
Electrochemical ammonia synthesis is being actively studied as a low temperature, low pressure alternative to the Haber-Bosch process. This thesis explores iridium as the catalyst for the electrochemical process, following a previous study of platinum catalysts. Specifically, the adsorption characteristics of intermediates involved in the synthesis reaction were studied on a theoretical 15-atom cluster of iridium. Characteristics studied here include bond energies, bond lengths, spin densities, and free and adsorbed vibrational frequencies for the following set of molecules: N2, N, NH, NH2, NH3, N2H, N2H2, N2H3, N2H4, H2O, and OH radical. Objective one was to generate useful information that will set the basis for a mechanistic study of the synthesis process. Objective two was to use these simulations to explore the use of dispersion-corrected Density Functional Theory methods that can model N2 adsorption – the key reactant for electrochemical ammonia synthesis via transition metal catalysis. Specifically, three methods were tested: hybrid B3LYP, a dispersion-corrected form B3LYP-D3, and semi-empirical B97-D3. The latter semi-empirical method was explored to increase the accuracy obtained in vibrational analysis as well as reduce computational time. Two lattice surfaces, (111) and (100), were compared. The adsorption energies were stronger on (100) and follow the trend EB3LYP > EB3LYP-D3 > EB97-D3 on both surfaces. In the conclusion of this thesis, recommendations are given on how this data may be used to support a future study in pursuit of a mechanism for ammonia synthesis on iridium.
Gerardine Botte (Advisor)
David Tees (Advisor)
68 p.
Chemical Engineering; Chemistry; Engineering; Physics
Density functional theory; Dispersion methods; Ammonia synthesis; Iridium catalyst; Ammonia adsorption

Recommended Citations

Citations

  • Grossman, E. F. (2019). Comparing B3LYP and its dispersion-corrected form to B97-D3 for studying adsorption and vibrational spectra in nitrogen reduction [Undergraduate thesis, Ohio University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ouhonors155628790845

    APA Style (7th edition)

  • Grossman, Esther. Comparing B3LYP and its dispersion-corrected form to B97-D3 for studying adsorption and vibrational spectra in nitrogen reduction. 2019. Ohio University, Undergraduate thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ouhonors155628790845.

    MLA Style (8th edition)

  • Grossman, Esther. "Comparing B3LYP and its dispersion-corrected form to B97-D3 for studying adsorption and vibrational spectra in nitrogen reduction." Undergraduate thesis, Ohio University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ouhonors155628790845

    Chicago Manual of Style (17th edition)

ouhonors155628790845
195
© 2019, all rights reserved.
This open access ETD is published by Ohio University Honors Tutorial College and OhioLINK.