- 标题
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Infrared Spectroscopy of Triatomics for Space Observation || Clathrate Nano-Cages
摘要： Determining the presence and evolution of molecular species and their physicochemical environment in astrophysical media makes high-resolution infrared spectroscopy a powerful investigative tool that would provide a great deal of information on how these molecules behave in their environments. In this chapter, we describe the theoretical models developed to analyze the absorption spectra of a triatomic molecule trapped in a clathrate nano-cage at very low temperatures. The Lakhlifi–Dahoo extended inclusion model allows the determination of the trapping site (cage structure type), position and movements of the molecule in its site. Frequency shifts due to the solid environment can be interpreted using an atom–atom potential model to describe the interaction between the clathrate matrix and the trapped molecule. Moreover, this inclusion model makes it possible to determine the IR spectra and the couplings with the atoms or molecules forming the nano-cage.
关键词： clathrate,nano-cage,inclusion model,infrared spectroscopy,astrophysical media,triatomic molecule
更新于2025-09-23 15:23:52
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Germanium-isotope-driven distortion and disorder in clathrate framework
摘要： We report a definitive evidence that germanium isotope effect triggers a noticeable cage distortion in n-type Ba8Ga16Ge30 (BGG) with complete substitution of isotope Ge-76. Further extended X-ray absorption fine structure technique reflects a large disorder in the cages of the sample, although no accompanying obvious changing in distance of Ge-Ga/Ge is demonstrated. Hence, we suggest that the cumulative cage distortion originates from the variation of bond angle instead of bond length. Moreover, the intensive electron-phonon scattering is dominated by the isotope effect. These findings highlight atomic isotope engineering for modifying crystal structure and possibly even thermoelectric performance.
关键词： Clathrate,EXAFS,Isotope effect,Thermoelectrics
更新于2025-09-23 15:22:29
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Van der Waals Integration of Bismuth Quantum Dots–Decorated Tellurium Nanotubes (Te@Bi) Heterojunctions and Plasma‐Enhanced Optoelectronic Applications
摘要： Crystallization is relevant to many disciplines, and the control of crystallization of molecules is of importance to a great range of technological applications. It has been well established that a variety of surfaces can serve as possible nucleation sites for heterogeneous crystallization. However, it is still unknown what features of such system may be crucial and whether just a single molecule might serve as a nucleation site for crystallization. Therefore, to probe this question, we have investigated the nucleation of a prototypical multicomponent crystal, clathrate hydrates. As multicomponent crystalline compounds, clathrate hydrates have drawn considerable attention because of their scientific and industrial importance. Clathrate hydrates can occur in several possible structures, where the size of guest molecules and their ability to fit into water cages is a crucial factor. Despite the fact that in most applications, for example in oil?gas pipelines, clathrate hydrates form from gas mixtures that feature a variety of sizes of guest molecules, the possible roles of these species in hydrate formation has remained essentially unexplored. Herein, we investigate the impact of the presence of 2,2-dimethylbutane (DMB) on the nucleation of methane hydrate. Our simulation results provide clear evidence that DMB can serve as a nucleation site and can promote the formation of methane hydrates. The low mobility of the DMB molecule, and the longer residence time and hydrate-like structure of water molecules in its hydration shell appear as important contributors to its behavior. These results demonstrate that the presence of a somewhat larger hydrocarbon in low concentration can significantly impact hydrate nucleation and hence have immediate impact in, for example, flow assurance in oil?gas pipelines. More generally, the results presented herein indicate that single molecules in an otherwise homogeneous solution can promote crystal nucleation by stabilizing early stage structural fluctuations in the liquid.
关键词： crystallization,clathrate hydrates,molecular dynamics simulations,methane hydrate,2,2-dimethylbutane,nucleation
更新于2025-09-11 14:15:04