In this award, funded by the Experimental Physical Chemistry Program of the Chemistry Division, Profs. Robert L. Vold and Gina Hoatson from the College of William and Mary and their graduate and undergraduate student colleagues will develop models for simulating slow molecular motion to include more realistic motional models, to apply them to experiments that are important for very high magnetic resonance, and to make the dynamic simulation and data fitting procedures easily accessible and freely-available to non-specialists. Parts of this research will also involve collaboration with the X-ray diffraction group of Prof. J. Stezowski at the University of Nebraska.
Solid State Nuclear Magnetic Resonance Spectroscopy is a powerful technique that allows scientists to determine the structures and motions of molecules in solids. The work of Prof. Vold, Prof. Hoatson and their research colleagues and research students will enable scientists to study a broader range of materials, and to analyze some of the very slow motions that take place in important classes of materials. In addition to the broader scientific impact of the proposed work, the students being trained in this project will be exposed to unique interdisciplinary research. One product from this research will be a set of software programs that the PIs will freely distribute via their website.
Nuclear magnetic resonance (NMR) refers to the manner in which low energy, radiofrequency electromagnetic radiation can be absorbed at discrete frequencies by most atomic nuclei when placed in a strong, constant magnetic field. Since the absorption frequencies are characteristic of the microscopic, immediate surroundings of the atomic nuclei, analysis of the absorption line shape can provide unique information about how the bulk properties of materials are related to their microscopic, atomic structure. Moreover, the rate at which energy absorbed at a particular frequency is dissipated ( i.e., the "relaxation rate") can be analyzed mathematically to reveal information about molecular motion on time scales ranging from seconds to picoseconds. Applications of the powerful methodology of NMR in fields as diverse as magnetic resonance imaging, biological structure-function relations, and optimization of engineering polymers are widespread and well known. Work performed at the College of William and Mary, with support from NSF Grant CHE0713819 "Quantitative Studies of Molecular Dynamics in Solids by Nuclear Magnetic Resonance of Quadrupolar Nuclei", was aimed at developing new, user-friendly algorithms for analyzing NMR line shapes and relaxation data so that researchers with diverse backgrounds and areas of specialization could take maximum advantage of the latest NMR methodology. In particular, a platform-independent software program, EXchange Program for Partially RElaxed Spin Systems (EXPRESS), was designed, implemented and posted on the principal investigators web site. Intellectual Merit: A unique feature of EXPRESS is its ability to simulate NMR line shapes not only for nuclei of spin ½ and spin 1, but also for all quadrupolar nuclei with higher spin quantum numbers including 3/2, 5/2, 7/2 and 9/2. This is important because many technologically important devices, such as lithium ion batteries, ferroelectric computer memories, and ultrasonic transducers and actuators, rely on precise control of the properties of advanced materials with quadrupolar nuclei. Thus, using EXPRESS software to analyze NMR data of scandium (a quadrupolar nucleus with spin 7/2) and niobium (spin 9/2), we are able to identify specific local arrangements of ions in a disordered crystal lattice that are responsible for the remarkable properties of high performance ferroelectric materials. In other laboratories, EXPRESS is being used to characterize dynamics in battery materials as revealed by NMR of lithium (spin 3/2) and oxygen-17 (spin 5/2). In addition, EXPRESS is being used in several laboratories around the world to characterize dynamics in a wide variety of biologically important materials, based on analysis of solid-state deuteron NMR measurements. A screen shot showing how EXPRESS can be used in the latter manner is shown in the accompanying figure. Broader Impact: During the course of developing a graphical user interface that is easy for non-specialists to master, we settled on the idea that each identifiable subset of input parameters (e.g., those related to spectrometer controls, those related to motional rates, those related to static spin interactions, and those related to details of numerical analysis) should have its own input screen, accompanied by a "HELP" button. Pressing the help button puts the screen into instructional mode, in which activating any other control on that screen will not actually perform the indicated function, but instead will invoke an on-screen tutorial that explains the role of that control and provides tips on how best to use it., as well as a synopsis of the underlying theory. This feature of our software has proved to be an extremely popular and useful educational tool; it is used routinely in our laboratory at the College of William and Mary to introduce new graduate students to the intricacies of analyzing NMR line shapes and relaxation rates. The pedagogical advantages of research-grade software with control-specific tutorial help screens ( in lieu of a traditional software manual) are by no means limited to EXPRESS or any other discipline-specific application packages. It is possible that this highly interactive way of conveying the latest research advances to students at all levels of expertise could provide an educationally effective and very economical alternative to the ever-increasing cost of scientific textbooks.
