Ca₁₂Al₁₄O₃₃ (C12A7, 12CaO·7Al₂O₃, or ${\left[{\mathrm{Ca}}_{12}{\mathrm{Al}}_{14}{\mathrm{O}}_{32}\right]}^{2+}:{\mathrm{O}}^{2-}$ ) is a material with a clathrate cage framework, positively charged and stabilized by anions occluded within 17% of the cages. The occluded anion is modular and can be elemental, polyatomic, and electronic in nature. This review focuses on the electride C12A7 ( ${\left[{\mathrm{Ca}}_{24}{\mathrm{Al}}_{28}{\mathrm{O}}_{64}\right]}^{4+}:\left(4*\partial \right){\mathrm{e}}^{-}\left(2-\partial \right){\mathrm{O}}^{2-}$ ), where O₂₋ anions are replaced with electrons, and compliments previous structural and electronic property reviews to illuminate the structure–property relationships. Electride formation is updated with new findings in carbonaceous reduction methods. Most importantly, an extensive compilation of cationic doped C12A7 isostructural compounds is presented as motivation to study doped C12A7 electrides. Cationic dopants have profound impacts on the electronic properties due to changes in the density of states, localized electron behavior, and structural distortions.

Structure-property relations in meaoscopic BaTiO₃ and PbTiO₃ are reviewed from the stand-point of effects of crystallite size on intrinsic behavior using the Landau-Ginzburg-Devonshire formalism. Experimental results based on x-ray diffrdctometry and quantitative calorimetry indicate that the critical crystallite sizes (CCS) for the stabilization of the cubic paraelectric phase in BaTiO₃ and PhTiO₃ are in the vicinity of 67 and 15 nm, respectively. Thc CCS scales inversely with the cubic-tetragonal transition temperature (Ttr). The depression in Ttr in PbTiO₃ is -15 (C with decreasing crystallite size (CS). A decrease in Ttr for BaTiO₃ was not observed. Both systems preserve their first order phase transformation characteristics with reduced CS. Electrostrictive coefficients were determined as a function of CS and were found to exhibit a pronounced increase with decreasing CS. The increase in the elcctrobtrictive coefficients offsets the decrease in spontaneous polarization and results in an increase in piezoelectric moduli suggesting that strong piezoelectric activity could indeed be observed in the mesoscopic size range

A vast source of methane is found in gas hydrate deposits, which form naturally dispersed throughout ocean sediments and arctic permafrost. Methane may be obtained from hydrates by exchange with hydrocarbon byproduct carbon dioxide. It is imperative for the development of safe methane extraction and carbon dioxide sequestration to understand how methane and carbon dioxide co-occupy the same hydrate structure. Pair distribution functions (PDFs) provide atomic-scale structural insight into intermolecular interactions in methane and carbon dioxide hydrates. We present experimental neutron PDFs of methane, carbon dioxide and mixed methane-carbon dioxide hydrates at 10 K analyzed with complementing classical molecular dynamics simulations and Reverse Monte Carlo fitting. Mixed hydrate, which forms during the exchange process, is more locally disordered than methane or carbon dioxide hydrates. The behavior of mixed gas species cannot be interpolated from properties of pure compounds, and PDF measurements provide important understanding of how the guest composition impacts overall order in the hydrate structure.