Calcium silicate hydrate (C-S-H) synthesized by a hydrothermal process from lime and siliceous materials was oven-dried and compressed into compacts. The microstructure and compaction properties of the resulting powders were characterized. The results show that the powders containing an amorphous structure become hardened compacts immediately after compression. Compacts with high strength but a relatively lower bulk density were produced. Amorphous C-S-H plays a key role in the bonding formation during powder compaction. According to the Heckel plots, particle rearrangement and plastic deformation were involved in the compaction of C-S-H powders. Point contact between C-S-H particles due to particle rearrangement dominates at a low compression pressure (i.e., 60 MPa), which results in surface contact. Consequently, a solid bridge forms, and the strength of compacts increases rapidly. These findings provide novel insight into the utilization of materials containing amorphous calcium silicate hydrate.

The structure, stability, charge transfer, and chemical bonding properties of palladium-doped magnesium clusters, PdMg n (n = 2-20), are comprehensively researched by CALYPSO software within first-principles DFT computations. It is shown that the cluster structure evolved from a tetrahedral-based structure to a cage-like structure, and interestingly, the single Pd atom always immerses in the Mg n clusters except for PdMg 2 and PdMg 3. Stability studies indicate that PdMg 4 , PdMg 7 , PdMg 10 , and PdMg 15 clusters have relative robust stability and can be identified as 'magic' clusters. Most importantly, chemical bonding studies reveal that Pd-Mg is always non-covalent bond (closed-shell) interaction in all PdMg n (n = 2-20) clusters, and PdMg 6 and PdMg 7 are the critical sizes at which Mg-Mg covalent interactions occur. The geometric structure database of transition metal-doped Mg clusters will be enriched by this study, and it also provides, at least theoretically, new members of cage-like structures for magnesium-based hydrogen storage nanomaterials.

Beryllium doped small-sized magnesium and its ion clusters are fully studied in this work. CALMPSO software was used to search for BeMg^Q _n (Q = 0, ±1, n = 2–12) clusters’ structures. The structural optimization with density functional theory (DFT) of BeMg^Q _n clusters was performed by two functionals B3PW91/6-311G(d,p) and PBE0/6-311G(d,p). Although the structures of clusters are diverse, their geometries with 3D structures can be summarized as two types of growth mechanism based on tetrahedron and tower-like. Calculations of the size dependence of the lowest energy state of BeMg^Q _n clusters using the two functionals, including average binding energy, second-order energy difference, HOMO–LUMO energy gap, VIP and VEA, coincidentally indicate that BeMg⁰ ₉, BeMg⁺¹ ₉ and BeMg⁻¹ ₈ are the local most stable clusters. For providing theoretical guidance for future experimental observations, the theoretical computations and simulations of BeMg⁻¹ _n clusters’ PES and BeMg^Q _n (Q = 0, ±1, n = 2–12) clusters’ IR and Raman spectra were performed. Finally, ELF, MO and DOS analyses of the local most stable clusters were carried out, and it was found that their stability mainly originated from the σ-type covalent bond formed by the interaction between the s- and p-orbitals of Be and Mg atoms.