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K-edge X-ray absorption (XAS), emission (XES), and photoelectron(XPS) spectra of nitrogen doped along graphene edges are systematicallyinvestigated by using first-principles methods. In this study we consideredpyridinium-like, pyridine-like, cyanide-like, and amine-like nitrogensat armchair and zigzag edges and pyrrole-like nitrogen at armchairedge as well as graphite-like nitrogen at graphene interior site.Our results indicate that nitrogen configuration and its location(armchair or zigzag edge) in nitrogen-doped graphene can be identifiedvia the spectral analysis. Furthermore, some controversial spectralfeatures observed in experiment for N-doped graphene-like materialsare unambiguously assigned. The present analysis gives an explanationto the reason why the peak assignment is usually made differentlybetween XPS and XAS. [ABSTRACT FROM AUTHOR]

We investigate the relationship between intramolecular rotational dynamics and molecular and crystal structure in 4,4'-dimethoxyoctafluorobiphenyl. The techniques are electronic structure calculations, X-ray diffractometry, and (1)H and (19)F solid state nuclear magnetic resonance relaxation. We compute and measure barriers for coupled methyl group rotation and methoxy group libration. We compare the structure and the structure-motion relationship in 4,4'-dimethoxyoctafluorobiphenyl with the structure and the structure-motion relationship in related compounds in order to observe trends concerning the competition between intramolecular and intermolecular interactions. The (1)H spin-lattice relaxation is nonexponential in both the high-temperature short-correlation time limit and in the low-temperature long-correlation time limit, albeit for different reasons. The (19)F spin-lattice relaxation is nonexponential at low temperatures and it is exponential at high temperatures.

The molecular and crystal structure of 3-(trifluoromethyl)phenanthrene has been determined by X-ray diffraction. The structure of the isolated molecule has been calculated using electronic structure methods at the HF/3-21G, HF/6-31G, MP2/6-31G and B3LYP/6-31G levels. The potential energy surfaces for the rotation of the CF3 group in both the isolated molecule and cluster models for the crystal were computed using electronic structure methods. The barrier height for CF3 rotation in the isolated molecule was calculated to be 0.40 kcal mol(-1) at B3LYP/6-311+G//B3LYP/6-311+G. The B3LYP/6-31G calculated CF3 rotational barrier in a 13-molecule cluster based on the X-ray data was found to be 2.6 kcal mol(-1). The latter is in excellent agreement with experimental results from the NMR relaxation experiments reported in the companion paper (Beckmann, P. A.; Rosenberg, J.; Nordstrom, K.; Mallory, C. W.; Mallory, F. B. J. Phys. Chem. A 2006, 110, 3947). The computational results on the models for the solid state suggest that the intermolecular interaction between nearest neighbor pairs of CF3 groups in the crystal accounts for roughly 75% of the barrier to rotation in the solid state. This pair is found to undergo cooperative reorientation. We attribute the CF3 reorientational disorder in the crystal as observed by X-ray diffraction to the presence of a pair of minima on the potential energy surface and the effects of librational motion.