http://hdl.handle.net/1957/20456 2013-06-20T05:26:32Z http://hdl.handle.net/1957/37996 Structural and magnetic investigation of Fe3+ and Mg2+ substitution into the trigonal bipyramidal site of InGaCuO4 Grajczyk, Rosa; Berthelot, Romain; Muir, Sean; Sleight, A. W.; Subramanian, M. A. See article for Abstract. This is the author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by Elsevier and can be found at: http://www.journals.elsevier.com/journal-of-solid-state-chemistry/. 2013-03-01T00:00:00Z http://hdl.handle.net/1957/37891 Fracture Toughness of Co4Sb12 and In0.1Co4Sb12 Thermoelectric Skutterudites Evaluated by Three Methods Eilertsen, James; Subramanian, M. A.; Kruzic, J. J. Interstitially filled skutterudites are a promising class of state-of-the-art thermoelectric materials. Although thermoelectrics are exposed to significant thermal stresses, little information is known about the fracture toughness of interstitially doped skutterudites. This work explores the fracture toughness of undoped Co₄Sb₁₂ and indium doped In₀.₁Co₄Sb₁₂ skutterudites using three methods: 1) Vickers indentation fracture (VIF), 2) Vickers indent crack opening displacement (COD), and 3) single-edge vee-notched bend (SEVNB) in 4-point flexure. Indium addition to the icosahedral void-sites is verified by an observed increase in the crystal lattice parameter and strongly enhanced thermoelectric properties in the indium-doped samples. Fracture toughness values for Co₄Sb₁₂ and interstitially doped In₀.₁Co₄Sb₁₂ were found to be identical using both the COD and SEVNB methods indicating no interstitial embrittlement occurs due to indium void-site filling. Furthermore, it was found that there is no significant extrinsic toughening by crack bridging or other mechanisms and the toughness was insensitive to grain size variations. Fracture toughness values derived from the Vickers indentation fracture (VIF) method did not agree with the other two methods and it is recommended that that method be avoided. The results indicate that the fracture toughness of skutterudites may be, at least in some cases, significantly lower (~0.5 MPa√m) than previously reported and there may be concern over the durability of skutterudite-based power-producing thermoelectric modules if care is not taken to ensure adequate toughness. This is the author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by Elsevier and can be found at: http://www.journals.elsevier.com/journal-of-alloys-and-compounds/. 2013-03-05T00:00:00Z http://hdl.handle.net/1957/37714 Probing structural evolution along multidimensional reaction coordinates with femtosecond stimulated Raman spectroscopy Frontiera, Renee R.; Fang, Chong; Dasgupta, Jyotishman; Mathies, Richard A. Mapping out multidimensional potential energy surfaces has been a goal of physical chemistry for decades in the quest to both predict and control chemical reactivity. Recently a new spectroscopic approach called Femtosecond Stimulated Raman Spectroscopy or FSRS was introduced that can structurally interrogate multiple dimensions of a reactive potential energy surface. FSRS is an ultrafast laser technique which provides complete time-resolved, background-free Raman spectra in a few laser shots. The FSRS technique provides simultaneous ultrafast time (~50 fs) and spectral (~8 cm⁻¹) resolution, thus enabling one to follow reactive structural evolutions as they occur. In this perspective we summarize how FSRS has been used to follow structural dynamics and provide mechanistic detail on three classical chemical reactions: a structural isomerization, an electron transfer reaction, and a proton transfer reaction. This is the author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by The Royal Society of Chemistry and can be found at: http://pubs.rsc.org/en/journals/journalissues/cp. 2012-01-01T00:00:00Z http://hdl.handle.net/1957/37452 Resonantly enhanced multiphoton ionization and zero kinetic energy photoelectron spectroscopy of Benzo[e]pyrene Harthcock, Colin; Zhang, Jie; Kong, Wei We report zero kinetic energy (ZEKE) photoelectron spectroscopy via resonantly enhanced multiphoton ionization (REMPI) for benzo[e]pyrene. Extensive vibronic coupling between the first electronically excited state and a nearby state allows b₂ symmetric modes to be observed which would normally be Franck-Condon (FC) disallowed. These vibronic modes are comparable in intensity to the FC allowed a₁ modes. Gaussian 09 is able to qualitatively simulate the vibronic spectra of the REMPI and the ZEKE experiment using density functional methods. The ZEKE spectra demonstrate propensity in preserving the vibrational excitation of the intermediate electronic state. These results suggest a remarkable structural stability of BeP in accommodating the additional charge. This is the author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by Elsevier and can be found at: http://www.journals.elsevier.com/chemical-physics-letters/. 2013-01-29T00:00:00Z