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Spectra of parametric X-radiation (PXR) in the range of anomalous dispersion of atoms of a crystallographic unit cell are theoretically analyzed. Characteristics of PXR are calculated for both ultrarelativistic (E ≥ 50 MeV) and non-relativistic (E ... 100 keV) electrons interacting with complex organic crystals. The analysis of the PXR angular distribution is shown to permit the realization of the anomalous scattering method for the direct measurement of structure amplitude phases. [ABSTRACT FROM AUTHOR]

Comparative X-ray diffraction studies at different temperatures are used to complement the information usually extracted from 'single-point' charge-density studies. The response of soft bonds against (temperature driven) changes of the crystalline environment might be indicative of some intramolecular mode associated with an incipient bonding. This is in fact confirmed for the anion [FeCo(CO)8]- in the [(Ph3P)2N]+ salt. In contrast, the [Crk2H(CO)10]- anion, whose conformation is known to strongly depend on the counterion, is actually insensitive to T variations in the [K(C18H36N2O6)]+ salt. [ABSTRACT FROM AUTHOR]

Provides information on subscription rates and prices for crystallography journals. "Acta Crystallographica Section A: Foundations of Crystallography"; "Acta Crystallographica Section B: Structural Science"; "Acta Crystallographica Section C: Crystal Structure Communications."