Complete miscibility of the intermetallic phases (IPs) SrGa2 and BaGa2 forming the solid solution Sr(1-x)Ba(x)Ga2 is shown by means of X-ray diffraction, thermoanalytical and metallographic studies. Regarding the distances of Sr/Ba sites versus substitution degree, a model of isolated substitution centres (ISC) for up to 10% cation substitution is explored to study the influence on the Ga bonding situation. A combined application of NMR spectroscopy and quantum mechanical (QM) calculations proves the electric field gradient (EFG) to be a sensitive measure of different bonding situations. The experimental resolution is boosted by orientation-dependent NMR on magnetically aligned powder samples, revealing in first approximation two different Ga species in the ISC regimes. EFG calculations using superlattice structures within periodic boundary conditions are in fair agreement with the NMR spectroscopy data and are discussed in detail regarding their application on disordered IPs.

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The durability of historic wall paintings is highly dependent on environmental influences such as moisture ingress, salt crystallization and temperature changes. A fundamental understanding of dynamic transport processes in wall paintings is necessary to apply suitable conservation and restoration methods to preserve such objects with high cultural value. Non-invasive, mobile-NMR techniques with single-sided sensors, such as the NMR-MOUSE(®), enable to monitor the moisture content, transport and apparent diffusion constants in wall paintings. We investigated this technique by experiment and modeling to correlate salt crystallization, moisture transport and local diffusion in wall-painting samples. Moreover, the influence of different painting techniques (fresco and secco) and conservation/consolidation methods on moisture transport and diffusion is discussed. The results are compared with results from field measurements on real fresco paintings in Casa del Salone Nero and the Villa of the Papyri, Herculaneum, Italy.

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