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BackgroundThe testing of theoretical models with experimental data is an integral part of the scientific method, and a logical place to search for new ways of stimulating scientific productivity. Often experiment/theory comparisons may be viewed as a workflow comprised of well-defined, rote operations distributed over several distinct computers, as exemplified by the way in which predictions from electronic structure theories are evaluated with results from spectroscopic experiments. For workflows such as this, which may be laborious and time consuming to perform manually, software that could orchestrate the operations and transfer results between computers in a seamless and automated fashion would offer major efficiency gains. Such tools also promise to alter how researchers interact with data outside their field of specialization by, e.g., making raw experimental results more accessible to theorists, and the outputs of theoretical calculations more readily comprehended by experimentalists.ResultsAn implementation of an automated workflow has been developed for the integrated analysis of data from nuclear magnetic resonance (NMR) experiments and electronic structure calculations. Kepler (Altintas et al. 2004) open source software was used to coordinate the processing and transfer of data at each step of the workflow. This workflow incorporated several open source software components, including electronic structure code to compute NMR parameters, a program to simulate NMR signals, NMR data processing programs, and others. The Kepler software was found to be sufficiently flexible to address several minor implementation challenges without recourse to other software solutions. The automated workflow was demonstrated with data from a [Formula: see text] NMR study of uranyl salts described previously (Cho et al. in J Chem Phys 132:084501, 2010).ConclusionsThe functional implementation of an automated process linking NMR data with electronic structure predictions demonstrates that modern software tools such as Kepler can be used to construct programs that comprehensively manage complex, multi-step scientific workflows spanning several different computers. Automation of the workflow can greatly accelerate the pace of discovery, and allows researchers to focus on the fundamental scientific questions rather than mastery of specialized software and data processing techniques. Future developments that would expand the scope and power of this approach include tools to standardize data and associated metadata formats, and the creation of interactive user interfaces to allow real-time exploration of the effects of program inputs on calculated outputs.

Fluorine-19 magnetic shielding tensors have been measured in a series of actinide tetrafluorides (AnF4) by solid state nuclear magnetic resonance spectroscopy. Tetravalent actinide centers with 0–8 valence electrons can form tetrafluorides with the same monoclinic structure type, making these compounds an attractive choice for a systematic study of the variation in the electronic structure across the 5f row of the Periodic Table. Pronounced deviations from predictions based on localized valence electron models have been detected by these experiments, which suggests that this approach may be used as a quantitative probe of electronic correlations. [ABSTRACT FROM AUTHOR]

Author(s): Ian Farnan (corresponding author) [1]; Herman Cho [2]; William J. Weber [2] There are large amounts of heavy α-emitters in nuclear waste and nuclear materials inventories stored in various [...]

Evidence for boron in both trigonal and tetrahedral coordination has been found in 11B magic-angle-spinning (MAS) nuclear magnetic resonance (NMR) spectra of natural, inclusion-free specimens of aluminum-rich lithian tourmaline from granitic pegmatites.

2H variable-temperature solid-state nuclear magnetic resonance spectroscopy was used to study the dynamics and orientations of terephthalate (TA) anions in mixed-anion hydrotalcite-like compounds. An X-ray diffraction of the hydrotalcite-like compounds samples used in the study suggested that there were at least two interlayer regions. Results also indicated that the dynamics and orientations of terephthalate (TA) anions is influenced mainly by the presence of CO(sub 3)(super 2-) anions in the interlayer areas rather than the layer charge.

Analyses of garnets with low levels of OH, including a colorless, pale orange grossular sample from Asbestos, Quebec, and a colorless grossular sample from Lelatema Hills, Tanzania, reveal major cluster sizes of four and two protons, respectively, in the hydrogrossular powder and the Tanzania garnet. A mixture of two proton and four proton clusters is evident in the colorless grossular sample from Asbestos. Solid-state proton NMR spectroscopy is used for the analysis.

A combined theoretical and solid-state 17O nuclear magnetic resonance (NMR) study of the electronic structure of the uranyl ion UO22+ in (NH4)4UO2(CO3)3 and rutherfordine (UO2CO3) is presented, the former representing a system with a hydrogen-bonding environment around the uranyl oxygens and the latter exemplifying a uranyl environment without hydrogens. Relativistic density functional calculations reveal unique features of the U–O covalent bond, including the finding of 17O chemical shift anisotropies that are among the largest for oxygen ever reported (>1200 ppm). Computational results for the oxygen electric field gradient tensor are found to be consistently larger in magnitude than experimental solid-state 17O NMR measurements in a 7.05 T magnetic field indicate. A modified version of the Solomon theory of the two-spin echo amplitude for a spin-5/2 nucleus is developed and applied to the analysis of the 17O echo signal of U 17O22+. [ABSTRACT FROM AUTHOR]

Several variable temperature experiments are conducted to study the molecular structure, as well as the dynamics of the low temperature phase of [NH.sub.3][BH.sub.3]. The analysis proves that the molecule retains its symmetric gas-phase structure in the orthorhombic unit cell.