Investigation on the Structure of a LiB3O5–Li2Mo3O10 High-Temperature Solution for Understanding the Li2Mo3O10 Flux Behavior

Raman spectroscopy study on terephthalamide crystal at high pressures

In this study, we have investigated the structural stability of terephthalamide (TPA) crystal at pressure from ambient to 15 GPa in the diamond anvil cell at room temperature by Raman spectroscopy. Assignment for the Raman vibration modes of TPA crystal at ambient conditions has been performed based on the density functional theory (DFT) calculations. Pressure-induced structural transition was monitored using in-situ Raman spectroscopy. Remarkable changes (including the appearance of new Raman peaks, disappearance of original Raman bands, discontinuous changes in the pressure dependence of some Raman wavenumbers at different pressures) in Raman spectra were observed at approximately 1.3 and 5.2 GPa, provided clear evidences for two pressure-induced phase transitions: phase I to phase II at ∼1.3 GPa, phase II to phase III at ∼5.2 GPa.

Ag2Mo3O10·2H2O nanorods under high pressure: In situ Raman spectroscopy

This work presents a pressure-dependent behavior of silver trimolybdate dihydrate (Ag₂Mo₃O₁₀·2H₂O) nanorods using in situ Raman scattering. The Ag₂Mo₃O₁₀·2H₂O nanorods were obtained by the hydrothermal method at 140 °C for 6 h. The structural and morphological characterization of the sample was performed by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). Pressure-dependent Raman scattering studies were performed on Ag₂Mo₃O₁₀·2H₂O nanorods up to 5.0 GPa using a membrane diamond-anvil cell (MDAC). The vibrational spectra under high pressure showed splitting and emergence of new bands above 0.5 GPa and 2.9 GPa. Reversible phase transformations under pressure were observed in silver trimolybdate dihydrate nanorods: Phase I - ambient phase (1 atm - 0.5 GPa) → Phase II (0.8 GPa - 2.9 GPa) → Phase III (above 3.4 GPa).

Raman and Density Functional Theory Studies of Li2Mo4O13 Structures in Crystalline and Molten States

The Li₂Mo₄O₁₃ melt structure and its Raman spectral characteristics are the key for establishing the composition-structure relationship of lithium molybdate melts. In this work, Raman spectroscopy, factor group analysis, and density functional theory (DFT) were applied to investigate the structural and spectral details of the H-Li₂Mo₄O₁₃ crystal and a Li₂Mo₄O₁₃ melt. Factor group analysis shows that the crystal has 171 vibrational modes (84A_g + 87A_u), including three acoustic modes (3A_u), six librational modes (2A_g + 4A_u), 21 translational modes (7A_g + 14A_u), and 141 internal modes (75A_g + 66A_u). All of the A_g modes are Raman-active and were assigned by the DFT method. The Li₂Mo₄O₁₃ melt structure was deduced from the H-Li₂Mo₄O₁₃ crystal structure and demonstrated by the DFT method. The results show that the Li₂Mo₄O₁₃ melt is made up of Li⁺ ions and Mo₄O₁₃^2- groups, each of which is formed by four corner-sharing MoO₃Ø/MoO₂Ø₂ tetrahedra (Ø = bridging oxygen). The melt has three acoustic modes (3A) and 54 optical modes (54A). All of the optical modes are Raman-active and were accurately assigned by the DFT method.

Structural studies of a Li2O·4B2O3 melt by high-temperature Raman spectroscopy and density functional theory

High-temperature Raman spectroscopy and density functional theory have been employed to study the Li₂O·4B₂O₃ melt structure; B₃O₄Ø₂ and B₃O₃Ø₃ six-membered rings were found to be the main anion groups present in the melt.