Atom-by-Atom Evolution of the Same Ligand-Protected Au 21 , Au 22 , Au 22 Cd 1 , and Au 24 Nanocluster Series

Li, Yingwei; Cowan, Michael J.; Zhou, Meng; Luo, Tian-Yi; Song, Yongbo; Wang, He; Rosi, Nathaniel L.; Mpourmpakis, Giannis; Jin, Rongchao

doi:10.1021/jacs.0c09110

Abstract

The Raman spectral behavior of N₂, CO₂, and CH₄in ternary N₂–CO₂–CH₄mixtures was studied from 22°C to 200°C and 10 to 500 bars. The peak position of N₂in all mixtures is located at lower wavenumbers compared with pure N₂at the same pressure (P)–temperature (T) (PT) conditions. The Fermi diad splitting in CO₂is greater in the pure system than in the mixtures, and the Fermi diad splitting increases in the mixtures as CO₂concentration increases at constantPandT. The peak position of CH₄in the mixtures is shifted to higher wavenumbers compared with pure CH₄at the samePTconditions. However, the relationship between peak position and CH₄mole fraction is more complicated compared with the trends observed with N₂and CO₂. The relative order of the peak position isotherms of CH₄and N₂in the mixtures in pressure–peak position space mimics trends in the molar volume of the mixtures in pressure–molar volume space. Relationships between the direction of peak shift of individual components in the mixtures, the relative molar volumes of the mixtures, and the attraction and repulsion forces between molecules are developed. Additionally, the relationship between the peak position of N₂in ternary N₂–CO₂–CH₄mixtures with pressure is extended to other N₂‐bearing systems to assess similarities in the Raman spectral behavior of N₂in various systems.

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