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This paper aims to investigate the adsorption of carbonic acid and water molecules on the (010) surface of γ‐dicalcium silicate (γ‐C2S) at an atomic scale using density functional theory (DFT) and ab initio molecular dynamics. It provides novel insights into the mechanism of carbonation on the surface of γ‐C2S. The electrons transfer and interfacial reactions between the carbonic acid (H2CO3) molecule and the γ‐C2S surface are characterized by adsorption configuration, bond order, electron density difference, and partial density of states. There exist strong interactions between H2CO3 and γ‐C2S surface, including two types of chemical adsorption and one type of physical adsorption. This work confirms that water in the carbonation of γ‐C2S is to react with CO2 to provide the reactants, and protons transfer of the carbonic acid molecule plays a crucial role in the carbonation process. The adsorption of the carbonic acid molecule is more favorable with respect to that of the water molecule, which may be the initial step of the carbonization of γ‐C2S. [ABSTRACT FROM AUTHOR]

Brownmillerite‐type oxides are a large family of structural and functional materials that are of great concern. In this study, the occupancy mechanism of Fe and Al ions in brownmillerite Ca2FeAlO5 is revealed and the specific configuration of Ca2FeAlO5 is proposed for the first time. Through the energy analysis of a series of conjectured models based on well‐defined ab initio calculations, we find that the distribution of Al and Fe in Ca2FeAlO5 follows the "homogeneous layer principle", namely, Al and Fe tend to form homogeneous octahedral layers or tetrahedral chains rather than mixed layers or chains of two elements along the b axis. The theoretical Ca2FeAlO5 structure with specific atomic occupancy is proposed based on energy analysis and previous experiments, which is of fundamental significance for further study of its physical and chemical properties. Moreover, the influence of entropy increment on the stability of Ca2FeAlO5 crystal is clarified, which paves the way to investigate the structures and properties of Ca2FeAlO5 and other brownmillerite members. [ABSTRACT FROM AUTHOR]

(1− x) BaTiO3- x BiYO3 [(1− x) BT- x BY] polycrystalline ceramics were prepared by solid-state reaction method. The ceramics are in tetragonal phase when x ≤ 0.04, transform to pseudocubic at x ≥ 0.06, showing a classic ferroelectric to relaxor transition at x = 0.06, where the phase transition temperature was found to shift to higher temperature with increasing frequency. The dielectric permittivity peaks were analyzed by the modified Curie-Weiss law. Both parameters ΔTdiffuse and ΔTrelaxor were found to increase with increasing BY content, demonstrating a stronger relaxor characteristic. [ABSTRACT FROM AUTHOR]