Area of Interest
The detailed arrangement of atoms and ions in molecules and in crystalline materials
controls the physical and chemical properties of all matter. The experimental determination
of solid state composition and structure is accomplished unambiguously using x-ray
diffraction data from computer-controlled, single-crystal and polycrystalline powder
Diffraction data from pure single crystals can be transformed into highly accurate atomic positions. This transformation, together with detailed analysis of bond lengths, bond angles, conformation, and symmetry, is carried out using advanced computational techniques that include group theory, Fourier transforms, statistics, computer graphics, and database correlations using the Cambridge Crystal Database.
Single-crystal systems of current interest include organic compounds with pharmacological activity such as plant natural products and "designer-drugs." Inorganic compounds of current interest include organometallics and mixed metal oxides; interest in the latter stems from the tendency of some metal oxide Perovskites to act as high-temperature superconductors.
Diffraction data from a pure polycrystalline powder at both fixed and variable temperatures provides, at a minimum, quantitative identification of phases; coupled with the JCPDS Powder File, this "fingerprint" allows the exact composition of the material to be identified. Exceptionally high-quality data, coupled with advanced computational algorithms such as the Reitveld method, can result in ab initio structure determination similar to that achieved from single crystal x-ray diffraction data.
Complex polycrystalline mixtures produce complex diffraction patterns; these data, when subjected to advanced deconvolution, simulation, and pattern recognition techniques, yield quantitative information about the composition of the material. Systems of interest include doped metal oxides used as hydrocarbon-reforming catalysts and recyclable minerals used as building materials and for solid-waste disposal.
In addition to x-ray diffraction, additional experimental and theoretical methods are employed to characterize the chemical and physical properties of materials; these may include electronic and magnetic spectroscopies, electrochemistry, ab initio and semiempirical quantum chemical calculations, molecular mechanics, and high-resolution computer modeling.
Awards & Honors
Presidential Award for Excellence in Science, Mathematics and Engineering Mentoring
Fronczek, Frank R.; Delord, Terry J.; Watkins, Steven F.; Gueorguieva, Petia; Stanley, George G.; Zizza, Annegret S.; Cornelius, Jeffrey B.; Mantz, Yves A.; Musselman, Ronald L.. A Solid-State Spectral Effect in Eclipsed Tetracyanonickelates: X-ray Crystal Structure, Polarized Specular Reflectance Spectroscopy, and ZINDO Modeling of Sr[Ni(CN)4].5H2O, Rb2[Ni(CN)4].H2O, and Na2[Ni(CN)4].3H2O. Inorganic Chemistry, 2003, 42(22), 7026-7036
Steven F. Watkins. In the classroom: Applying the reaction table method for chemical reaction problems (stoichiometry and equilibrium). J. Chem. Education, 2003, 80(6), 658-661
Cornelius, Jeffrey B.; Trapp, Robert M.; Delord, Terry J.; Fronczek, Frank R.; Watkins, Steven F.; Orosz, Jill Jasin; Musselman, Ronald L.. One-Dimensional Collective Electronic Effects in the Helically Stacked Cs2[Ni(CN)4]H2O and Cs2[Pt(CN)4]H2O: X-ray Structure, Polarized Specular Reflectance, and ZINDO Calculations. Inorganic Chemistry, 2003, 42(9), 3026-3035
Liu, Yen Hsiang; Robbs, Steven L.; Fronczek, Frank R.; Watkins, Steven F.; Fischer, Nikolaus H.. A new polymorph of atranorin, a lichen paradepside. Acta Crystallographica, Section E Structure Reports Online, 2002, E58(8), 877-878