In this study, we investigated the protonation of the amine group in epoxy resins prepared using amine-based curing agents by theoretical methods. Density functional theory (DFT)based free-energy calculations of the corresponding deprotonation subreactions showed that the amine group of the epoxy resin is protonated at equilibrium depending on the location of the amine group when the epoxy resin is embedded in water under standard conditions. Additional DFT calculations demonstrate that the energetic barrier for breaking the ether bond of the epoxy resin is lowered by about 0.6 eV as a result of the cooperative effect of H 2 O dissociation and that the transition-state energy for breaking the amine group bond is lowered by about 0.4 eV after the protonation of the amine group. Comparing the transition-state energies, we predict that the bond breakage of the protonated amine groups is the principal process causing the weakening of epoxy resins under wet conditions.

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We investigate the electronic and magnetic properties of single-walled carbon nanotubes (SWNTs) filled with Fe nanowires, based on the spin-polarized density functional theory. We find that in the stable structure, the Fe-filled (3,3) and (5,0) SWNTs exhibit semiconducting properties, and the magnetic moment of Fe nanowires inside disappears. On the other hand, the Fe-filled (4,4), (5,5), (6,6) and (6,0) SWNTs, having larger radii, are metallic and exhibit ferromagnetic properties. The corresponding magnetic moment increases with increasing nanotube diameter.

We investigated the microscopic structure of FePtCu ternary ordered alloys from both theoretical and experimental points of view. From the theoretical viewpoint, first principles calculation was carried out based on the full-potential linear augmented plane wave method in order to obtain the electronic structure and magnetic anisotropy energy of the FePtCu ternary ordered alloy. From the experimental viewpoint, the ultraviolet photoelectron spectroscopy measurement was used to identify the Cu position in FePtCu ternary ordered alloy. From a comparison with the calculated density of states curve, it was found that the Fe site of FePt ordered alloy replaced the Cu. The theoretical and experimental results in this article support the mechanism proposed in terms of the thermodynamic considerations in our previous article.