Molecular dynamics simulations of the swollen membrane of perfluorinated ionomer, which is composed of poly(tetrafluoroethylene) backbones and perfluosulfonic pendant side chains, have been undertaken to analyze the static and dynamic properties of the water and the side chain in the membrane. The calculations were carried out for four different water contents, 5, 10, 20 and 40 wt %, at 358.15 K and 0.1 MPa. The results are summarized as follows: (1) The sulfonic acid is the unique site to which water molecules can bind, and the other sites in the pendant side chain have no bound water even at high water concentration. (2) Sulfonic acids aggregate in the short range within 4.6-7.7 A despite the electrostatic repulsion between them. In such aggregates, a water molecule bridges two sulfonic acids. (3) Pendant side chains prefer to orient perpendicular to the hydrophilic/hydrophobic interface, and long-range correlation of side chain orientations is observed at 20 and 40 wt % water uptake membranes. (4) In a low water uptake membrane, the dynamics of water is substantially restricted due to strong attractive interactions with acidic sites. In contrast, at high water content, even the water locating near the sulfonic acid is relatively mobile. The short residence time of the bound water reveals that such water can frequently exchange position with relatively free water, which locates in the center of water cluster, in highly swollen membranes.

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Different versions of a thermoelectric unicouple composed of p-type Ca2.7Bi0.3Co4O9 (Co-349) and n-type La0.9Bi0.1NiO3 (Ni-113) bulks were constructed using Ag paste containing p- and n-type oxide powders, prepared from the same bulks, for connection of the p and n legs, respectively. Internal resistance (RI) of the unicouple corrected using Ag paste containing 6 wt. % of the oxide powders is 26.2mΩ at 1073K in air and decreases with increasing temperature. Maximum output power (Pmax), evaluated using the formula Pmax=VO2∕4RI, (VO is open-circuit voltage), is 94mW at 1073K (ΔT=500K) and increases with temperature. This value corresponds to a volume power density of 0.66W∕cm3.

Intermolecular interaction energies of eight orientation CF4 dimers and seven orientation C2F6 dimers were calculated with electron correlation correction by the second-order Møller–Plesset perturbation (MP2) method. The D3d CF4 dimer and C2h C2F6 dimer have the largest binding energies. Electron correlation correction increases the attraction considerably, while the effects of electron correlation beyond MP2 are small. Electrostatic and induction energies are not large in all cases. This indicates that dispersion interaction is mainly responsible for the attraction. The calculated binding energy of the CF4 dimer (0.69 kcal/mol) is about 60% larger than that of the CH4 dimer (0.44 kcal/mol), while the binding energy of the C2F6 dimer (1.02 kcal/mol) is close to that of the C2H6 dimer (0.90 kcal/mol). The intermolecular separations (C⋯C distance) in the CF4 and CH4 dimers at the potential minima are close (4.0 and 3.8 Å, respectively), while the separation in the C2F6 dimer (4.8 Å) is appreciably larger than that in the C2H6 dimer (4.0 Å). The larger intermolecular separation in the C2F6 dimer reduces dispersion energy. Therefore the binding energies of the C2F6 and C2H6 dimers are not largely different. The molar volume of C2F6 is substantially larger than that of C2H6 due to bulky fluorine atoms. The small difference of the binding energies suggests that the large molecular volume of perfluoroalkanes is the cause of their small heats of vaporization per volume.

Silicate glasses have evolved from basic structural materials to enabling materials for advanced applications. In this article, we unravel the origin of the mixed alkali effect for alkali silicate 22.7R 2 O-77.3SiO 2 glasses (R = Na and/or K) by identifying the variation in the alkali ion location around the non-bridging oxygen atoms. To do so, we constructed a state-of-the art structural model, which reproduces both diffraction and NMR data with a particular focus on the behavior of the alkali ions. A novel topological analysis using persistent homology found that sodium-potassium silicate glass shows a significant reduction in large cavities as a result of the mixed alkali effect. Furthermore, a highly correlated pair arrangement between sodium and potassium ions around non-bridging oxygen atoms was identified. The potassium ions can be trapped in K-O polyhedra due to the increased bridging oxygen coordination; therefore, the correlated pair arrangement is likely the intrinsic origin of the mixed alkali effect.