Effects of Atomic Ordering of Interstitial Hydrogen on the Physical Properties of Host Metals

Physicochemical data on the infl uence of interstitial atoms of hydrogen isotopes on the properties of face-centred cubic, body-centred cubic and hexagonal close-packed metals are reviewed on the basis of statisticalthermodynamic theory of long- and short-range atomic order. Examples of the application of metal—hydrogen alloys are given.

FTIR-Based Crystallinity Assessment of Aragonite–Calcite Mixtures in Archaeological Lime Binders Altered by Diagenesis

Lime plaster and mortar are pyrotechnological materials that have been employed in constructions since prehistoric times. They may nucleate as calcite and/or aragonite under different environmental settings. In nature, aragonite and calcite form through biogenic and geogenic processes that lead to different degrees of atomic order. The latter is a result of defects in the crystal lattice, which affect the properties of crystals, including their interaction with infrared light. Using Fourier transform infrared spectrometry (FTIR) with the KBr pellet method, it is possible to exploit these differences and assess the degree of atomic order of aragonite and calcite crystals and thus their mechanisms of formation. Here we use FTIR to characterize the degree of short-range atomic order of a pyrogenic form of aragonite recently observed in experimental and archaeological lime binders. We show that pyrogenic aragonite has a unique signature that allows its identification in archaeological sediments and lime binders of unknown origin. Based on these results, we developed a new FTIR-based method to assess the integrity and degree of preservation of aragonite and calcite when they occur together in the same material. This method allowed a better assessment of the diagenetic history of an archaeological plaster and finds application in the characterization of present-day conservation materials, such as lime plaster and mortar, where different polymorphs may nucleate and undergo recrystallization processes that can alter the mechanical properties of binders.

Resonant Scattering in Condensed Matter, Experiments that Reveal Short to Long Range Atomic Order

After a historical introduction of the anomalous dispersion effect, the formalism used to investigate disordered materials using the resonant scattering of X-rays is exposed. As these experiments are sensitive to the experimental conditions, some experimental settings are discussed.