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High‐energy X‐ray diffraction was employed to study the structural characteristics of a set of C–S–H samples with 0.6 ≤ C/S ≤ 1.75. It has been observed that Si is tetrahedrally coordinated to O for all samples irrespective of chemical composition and the Ca–O coordination number gradually decreases from ~7 to ~6 with increasing C/S ratio. This suggests that the C–S–H structure evolves from a tobermorite‐like structure into a jennite‐like structure as a function of increasing C/S ratio as the interlayer space decreases from ~1.3 to ~1 nm. Evolution of these short‐ and medium‐range order structural characteristics in the C–S–H system is associated with the alteration of the Ca–O layers and silicate depolymerization with increasing C/S.

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A fundamental understanding of glass relaxation behavior is vital to the glass and polymer science communities. While prior work has focused on relaxation of first-order thermodynamic properties such as enthalpy and density, we present theoretical and experimental results showing that fluctuations in enthalpy and density relax nonmonotonically. These results provide direct evidence for dynamical heterogeneities and their close association with density fluctuations. Our results imply that density fluctuations, and hence light scattering, can be minimized through design of thermal history.

A combination of neutron and x-ray diffraction has been employed to study the compositional dependence of the atomic structures of GexAsxS100−2x glasses with S concentration varying between 33.3 and 70.0 at.%. The nearest-neighbor coordination numbers of Ge and As atoms are always found to be 4 and 3, respectively, irrespective of the glass composition. Ge and As atoms have primarily heteropolar bonding to S atoms in stoichiometric and S-excess glasses with x≤18.2. Low and intermediate levels of deficiency of S (20≤x≤25) are accommodated via the formation of homopolar As–As bonds while Ge atoms remain primarily bonded to four S atoms, resulting in As-rich regions in the glass structure. Ge starts to participate in metal–metal bonding only in the highly S-deficient glasses with 27.5≤x≤33.3. The intermediate-range order and its topological influence on atomic packing in these three compositional regions, in the order of increasing deficiency in S, are controlled by (a) a mixed GeS2 and As2S3 network, (b) the coexistence of a GeS2 network and As clusters, and (c) large Ge–As metal-rich regions. This evolution of the intermediate-range structure with composition is consistent with the corresponding variation of the position, intensity and width of the first sharp diffraction peak in the structure factor.