Theoretical Identification of Three C66 Fullerene Isomers and Related Chlorinated Derivatives by X-ray Photoelectron Spectroscopy and Near-edge X-ray Absorption Fine Structure Spectroscopy

Theoretical Study on the Structure and Spectral Properties of Several Classical and Non-Classical C76 Isomers and Their Newly Synthesized Derivatives

X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectra, as well as the ground-state electronic/geometrical structures of the newly discovered two non-classical isomers C₂-C₇₆(NC2) and C₁-C₇₆(NC3) with their derivatives C₂-C₇₆(NC2)(CF₃)₁₄ and C₁-C₇₆(NC3)Cl₂₄, as well as the non-IPR(isolated pentagon rule) isomer C₁-^#17418C₇₆ with its embedded metal fullerene U@C₁-^#17418C₇₆ have been calculated at the density functional theory (DFT) level. The electronic structure after chlorination is significantly different in the simulated X-ray spectrum. Both XPS and NEXAFS spectra reflect obvious isomer dependence, indicating that the "fingerprint" in X-ray spectroscopy can provide an effective means for the identification of the above-mentioned fullerene isomers. Time-dependent DFT was used to simulate the ultraviolet-visible absorption spectrum of U@C₁-^#17418C₇₆. The calculated results are in good agreement with the experimental consequence. This work reveals that theoretically simulated X-ray and UV-vis spectroscopy techniques can provide valuable information to help researchers explore the electronic structure of fullerenes and the identification of isomers in future experimental and theoretical fields.

Structural and Spectral Properties of a Nonclassical C66 Isomer with Its Hydrogenated Derivative C66H4 in Theory

X-ray photoelectron and near-edge X-ray absorption fine structure (NEXAFS) spectra, as well as the ground-state electronic/geometrical structures of a newly discovered nonclassical isomer C 2v -C66(NC), and two classical fullerene isomers C 2-#4466C66 and C s -#4169C66 with their hydrogenated derivatives [C 2v -C66H4(NC), C 2-#4466C66H4, and C s -#4169C66H4] have been calculated at the density functional theory (DFT) level. Significant differences were observed in the electronic structures and simulated X-ray spectra after hydrogenation. Simultaneously, both X-ray photoelectron and NEXAFS spectra reflected conspicuous isomer dependence, indicating that the "fingerprints" in the X-ray spectra can offer an effective method for identifying the above-mentioned fullerene isomers. The simulated ultraviolet-visible (UV-vis) absorption spectroscopy of C 2v -C66H4(NC) has also been generated by means of the time-dependent DFT method, and the calculations are well consistent with the experimental results. Consequently, this work reveals that X-ray and UV-vis spectroscopy techniques can provide valuable information to help researchers explore the fullerene electronic structure and isomer identification on the future experimental and theoretical fullerene domains.

Theoretical identification of buckyonion fullerene C20@C60 isomers by XPS and NEXAFS spectroscopy

The C 1s X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy of two buckyonion fullerene C₂₀@C₆₀ isomers were theoretically simulated by density functional theory (DFT) method. In this paper, we mainly investigated the relationship between spectroscopy and structure and obtained the spectral dependence on the structures with different symmetries. Our results showed that both XPS and NEXAFS spectra exhibited remarkable dependence on the molecular structures, thus these two spectroscopic techniques could be adopted to identify the two C₂₀@C₆₀ isomers effectively. Additionally, we found that the building block approach could not predict the spectra for C₂₀@C₆₀ isomers due to the strong interaction between the two layer cages. Finally, we studied the decompositions of the total spectra from carbon atoms in different local environments to analyse the origins of the main features.

Molecular inner-shell photoabsorption/photoionization cross sections at core-valence-separated coupled cluster level: Theory and examples

Oxygen, nitrogen, and carbon K-shell photoabsorption and photoionization cross sections have been calculated within core-valence-separated coupled cluster (CC) linear response theory for a number of molecular systems, namely, water, ammonia, ethylene, carbon dioxide, acetaldehyde, furan, and pyrrole. The cross sections below and above the K-edge core ionization thresholds were obtained, on the same footing, from L² basis set calculations of the discrete electronic pseudospectrum yielded by an asymmetric-Lanczos-based formulation of CC linear response theory at the CC singles and doubles (CCSD) and CC singles and approximate doubles (CC2) levels. An analytic continuation procedure for both discrete and continuum cross sections as well as a Stieltjes imaging procedure for the photoionization cross section were applied and the results critically compared.

Theoretical Identification of the Six Stable C84 Isomers by IR, XPS, and NEXAFS Spectra

Six stable C₈₄ isomers satisfying isolated pentagon rule (IPR) have been theoretically identified by infrared (IR), X-ray photoelectron (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectra. The XPS and NEXAFS spectra at the K-edge for all nonequivalent carbon atoms were simulated by the density functional theory method. NEXAFS spectra show stronger dependence than IR and XPS spectra on the six C₈₄ isomers, which can be properly used for isomer identification. Furthermore, spectral components of total spectra for carbon atoms in different local environment have been explored.

Theoretical identification of seven C80 fullerene isomers by XPS and NEXAFS spectroscopy

The molecular geometries and C1s NEXAFS spectra of seven IPR-satisfying isomers of fullerene C₈₀.