A generic definition of oxidation state (OS) is formulated: "The OS of a bonded atom equals its charge after ionic approximation". In the ionic approximation, the atom that contributes more to the bonding molecular orbital (MO) becomes negative. This sign can also be estimated by comparing Allen electronegativities of the two bonded atoms, but this simplification carries an exception when the more electronegative atom is bonded as a Lewis acid. Two principal algorithms are outlined for OS determination of an atom in a compound; one based on composition, the other on topology. Both provide the same generic OS because both the ionic approximation and structural formula obey rules of stable electron configurations. A sufficiently simple empirical formula yields OS via the algorithm of direct ionic approximation (DIA) by these rules. The topological algorithm works on a Lewis formula (for a molecule) or a bond graph (for an extended solid) and has two variants. One assigns bonding electrons to more electronegative bond partners, the other sums an atom's formal charge with bond orders (or bond valences) of sign defined by the ionic approximation of each particular bond at the atom. A glossary of terms and auxiliary rules needed for determination of OS are provided, illustrated with examples, and the origins of ambiguous OS values are pointed out. An electrochemical OS is suggested with a nominal value equal to the average OS for atoms of the same element in a moiety that is charged or otherwise electrochemically relevant.

Oxidation state (OS) is defined using ionic approximation of bonds. Two principal algorithms are outlined for OS determination in a chemical compound described by a Lewis formula or bond graph. Typical origins of ambiguous OS values are pointed out, and the relationship between OS and the d n electron configuration of transition metals is commented on.

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Radiative heat transfer (RHT) has a central role in entropy generation and energy transfer at length scales ranging from nanometres to light years. The blackbody limit, as established in Max Planck's theory of RHT, provides a convenient metric for quantifying rates of RHT because it represents the maximum possible rate of RHT between macroscopic objects in the far field-that is, at separations greater than Wien's wavelength. Recent experimental work has verified the feasibility of overcoming the blackbody limit in the near field, but heat-transfer rates exceeding the blackbody limit have not previously been demonstrated in the far field. Here we use custom-fabricated calorimetric nanostructures with embedded thermometers to show that RHT between planar membranes with sub-wavelength dimensions can exceed the blackbody limit in the far field by more than two orders of magnitude. The heat-transfer rates that we observe are in good agreement with calculations based on fluctuational electrodynamics. These findings may be directly relevant to various fields, such as energy conversion, atmospheric sciences and astrophysics, in which RHT is important.

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Oscail is a program for small-molecule crystallography which includes crystal morphology prediction and an interface to molecular modelling. The Oscail graphical user interface can drive SHELX and Superflip for structure solution and SHELXL for structure refinement. The lattice analysis includes hydrogen bonding, halogen bonding and van der Waals contact stacking. Other facilities include interactive bar charts of space-group frequencies in the Cambridge Structural Database, powder diffraction pattern calculation and reduced cell cluster analysis of structures. The graphics output includes thermal ellipsoid plots and rendered OpenGL and Raster3D photorealism in stills and movies. The molecular modelling includes quantum calculations (MOPAC, extended Hü ckel and density functional theory) and TINKER molecular mechanics.

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The crystal structures and crystal morphology of the mono-semicarbazone of 9,10-phenanthraquinone and nine of its solvates were examined to probe the mechanism of crystal growth of flat molecules. Three of the solvates were isomorphous, did not have stacked structures, and grew as blocks. Six of the solvates had stacked structures and grew as needles. A centroid distance based method for the detection of van der Waals (vdW) contact stacking is described. Nonflat carbamazepine (CBZ) forms I, III, and VI, 4-hydroxy-Nphenylbenzenesulfonamide, and a polymorph of 1,4-diphenyl-2H-cyclopenta[d]pyridazine all exhibited needle growth and have structures which maximize vdW contact stacking in the needle growth direction. The experimentally reported anisotropic dissolution of CBZ form I has been simulated using molecular dynamics. The intermolecular interactions have been analyzed using Gavezzotti's PIXEL program. Dispersion force interactions between the molecules are most important within the stacks. A crystal growth mechanism driven by the dispersion force rather than hydrogen bonding is suggested for both flat and nonflat molecules.