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Stimulated Raman scattering processes based on Raman crystals offer a simple and effective method to generate mid-IR lasers. However, currently available mid-IR Raman crystals are extremely scarce. Herein, a new type of mid-IR Raman crystal, BaGeO3, is reported. It crystallizes in the monoclinic space group C2/c with Ba2+ cations and [Ge3O9]6- rings as basic building units and features high transparency from 2.5 to 5.5 μm and a Raman response larger than that of diamond. The BaGeO3 crystal has 45 IR-active modes (22Au + 23Bu) and 42 Raman-active modes (20Ag + 22Bg). The wide mid-IR transparent window is attributed to the low phonon energy of the second-order IR-active Au ⊗ Bg mode. The strongest Raman band, located at 799 cm-1, arises from the symmetrically stretching vibration of the [Ge3O9]6- extra-ring Ge-O bonds. The findings provide new insights into the crystallographic and Raman spectroscopic characteristics of high-performance mid-IR Raman crystals.

Knowledge of the molecular-level structure of the Li2GeO3 melt is essential to understand its basic physicochemical properties. In this work, in situ Raman spectroscopy, factor group analysis, and ...

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 (84Ag + 87Au), including three acoustic modes (3Au), six librational modes (2Ag + 4Au), 21 translational modes (7Ag + 14Au), and 141 internal modes (75Ag + 66Au). All of the Ag 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 Mo4O132– groups, each of which is formed by four corner-sharing MoO3O/MoO2O2 tetrahedra (O = bridging oxygen). The melt has three acoustic modes (3A) and 54 o...

Stimulated Raman scattering processes based on Raman crystals offer a simple and effective method to generate mid-IR lasers. However, currently available mid-IR Raman crystals are extremely scarce. Herein, a new type of mid-IR Raman crystal, BaGeO

LiB3O5 is the most widely used nonlinear optical crystal. Li2Mo3O10 (a nominal composition) is a typical flux used to produce large-sized and high-quality LiB3O5 crystals. The structure of the LiB3O5–Li2Mo3O10 high-temperature solution is essential to understanding the flux behavior of Li2Mo3O10 but still remains unclear. In this work, high-temperature Raman spectroscopy combined with density functional theory (DFT) was applied to study the LiB3O5–Li2Mo3O10 solution structure. Raman spectra of a LiB3O5–Li4Mo5O17–Li2Mo4O13 polycrystalline mixture were recorded at different temperatures until the mixture melted completely. The solution structure was deduced from the spectral changes and verified by DFT calculations. When the mixture began to melt, its molybdate component first changed into the Li2Mo3O10 melt; meanwhile, the complicated molybdate groups existing in the crystalline state transformed into Mo3O102– groups, which are formed by three corner-sharing MoO3O–/MoO2O2 (O = bridging oxygen atom) tetrahe...

Knowledge of the molecular-level structure of the Li

The Li

LiB

Melt structures are essential to understand a variety of crystal growth phenomena of alkali-metal triborates, but have not been fully explored. In this work, Raman spectroscopy, coupled with the density functional theory (DFT) method, has been used to solve the CsB3O5 (CBO) melt structure. When the CBO crystal melts, the extra-ring B4–O bonds (the B–O bonds of BO4 groups, O = bridging oxygen atom) that connect two B3O3O4 rings (the basic boron–oxygen unit in the CBO crystal structure) break. As a result, the three-dimensional boron–oxygen network collapses to unique polymer-like [B3O4O2]n chains. On the basis of the optimized [B3O4O2]n chain model, the CBO melt Raman spectrum was calculated by the DFT method for the first time and the calculated results confirm that the [B3O4O2]n chain is the primary species in the CBO melt. These results also demonstrate the capability of the combined Raman spectral and DFT method for analyzing borate melt structures.