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Martin, Richard M. Trinkle, Dallas R. Stack, John D. Nayfeh, Munir H. Martin, Richard M. Beaudet, Todd D. 2011-01-21T22:51:15Z 2011-01-21T22:51:15Z 2013-01-22T11:00:14Z 2011-01-21T22:51:15Z 2010-12 This thesis research has successfully carried out a QMC study of hydrogen adsorption on Ti-ethylene molecular systems demonstrating reversible hydrogen adsorption on molecular TiH$_2$C$_2$H$_4$. This system is chosen as representative of larger carbon-transition-metal systems that may be relevant for practical hydrogen storage. To the author's knowledge this is the first study of hydrogen adsorption on transition metal systems by QMC methods. These systems present challenges in terms of a large number of possible molecular structures that are very close in energy, 3d states of transition elements that are difficult to treat, and molecular geometries that can be difficult to determine. Several studies are presented that demonstrate the suitability of QMC methods for this class of problem. A QMC study of hydrogen on benzene, which has already been published, tests the Slater-Jastrow (SJ) trial function against a more highly correlated Geminal trial function. The Slater-Jastrow form used here is shown to perform equivalently in measuring the small energy differences associated with physisorption. A series of tests is conducted on the Ti atom transition energies. QMC SJ results are found to be in excellent agreement with experiment so that significant cost savings can be achieved by using a pseudopotential for Ti. An extensive study on the TiH$_2$ system which is relevant to the final system studied is also presented. There a fixed-node DMC geometry optimization is conducted. It is shown the Perdew-Burke-Ernzerhof (PBE) functional for Density Functional Theory (DFT) is able to give geometries with energies that are within 1.5 mHa of the DMC optimal geometries. Also, it is consistently demonstrated throughout the work that QMC methods with SJ trial functions are only weakly dependent on the single-body theory used to produce the trial function. The primary results related to hydrogen storage are derived from studies on many structures of Ti-ethylene with up to 5 H$_2$ molecules. Ground and excited states are both considered. Formation energies are calculated and comparison is made to other work. It is shown that at least three hydrogen molecules can be adsorbed with energies in the range considered relevant for practical hydrogen storage. Item withdrawn by Mark Zulauf (zulauf@illinois.edu) on 2010-10-01T15:06:37Z Item was in collections: University of Illinois Theses & Dissertations (ID: 1) No. of bitstreams: 1 Beaudet_Todd.pdf: 1763711 bytes, checksum: e58bbc7654877c3f91aac34a058d8e73 (MD5) Made available in DSpace on 2011-01-21T22:51:15Z (GMT). No. of bitstreams: 2 Beaudet_Todd.pdf: 1763888 bytes, checksum: 3aa68f7639fc6767465436580378cd75 (MD5) license.txt: 4061 bytes, checksum: 3de58702fd6dc842b1c38c78e95524e0 (MD5) Item marked as restricted to the 'Administrator' Group (id=1) by William Ingram (wingram2@illinois.edu) on 2011-01-21T22:53:45Z Item is restricted until 2013-01-21T22:53:34Z Item reinstated by Sarah Shreeves (sshreeve@illinois.edu) on 2013-01-22T11:00:13Z Item was in collections: University of Illinois Dissertations and Theses (ID: 204) Dissertations and Theses - Physics (ID: 445) No. of bitstreams: 3 Beaudet_Todd.pdf.txt: 252302 bytes, checksum: 59bb4a05d667d8eb64f11e320d4d0c06 (MD5) Beaudet_Todd.pdf: 1763888 bytes, checksum: 3aa68f7639fc6767465436580378cd75 (MD5) license.txt: 4061 bytes, checksum: 3de58702fd6dc842b1c38c78e95524e0 (MD5) Item released from any restrictions by Sarah Shreeves (sshreeve@illinois.edu) on 2013-01-22T11:00:14Z http://hdl.handle.net/2142/18600 en Copyright 2010 by Todd D. Beaudet hydrogen storage hydrogen titanium ethylene benzene, titanium dihydride Adsorption transition metal Quantum Monte Carlo (QMC) Diffusion Monte Carlo (DMC) Density Functional Theory (DFT) Quantum Monte Carlo Study of Hydrogen Adsorption on Carbon and Transition Metal Systems Physics 1244 Physics 0240 University of Illinois at Urbana-Champaign Dissertation Ph.D. PHD:Physics -UIUC 10KS0240PHD