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Cage Isomers (cage + isomer)
Selected AbstractsCage Isomers of N14 and N16: Nitrogen Molecules that Are Not a Multipe of SixCHEMINFORM, Issue 7 2005Douglas L. Strout Abstract For Abstract see ChemInform Abstract in Full Text. [source] Entrapped Bonded Hydrogen in a Fullerene: the Five-Atom Cluster Sc3CH in C80CHEMPHYSCHEM, Issue 4 2007Matthias Krause Dr. Abstract The synthesis and characterisation of the new endohedral cluster fullerene Sc3CH@C80 is reported. The encapsulation of the first hydrocarbon cluster inside a fullerene was achieved by the arc burning method in a reactive CH4 atmosphere. The extensive characterisation by mass spectrometry (MS), high- pressure liquid chromatography (HPLC), 45Sc NMR, electron spin resonance (ESR), UV/Vis-NIR and Raman spectroscopy provided the experimental evidence for the caging of the five-atom Sc3CH cluster inside the C80 cage isomer with icosahedral symmetry. The proposed new structure was confirmed by DFT calculations, which gave a closed shell and large energy gap structure. Thus a pyramidal Sc3CH cluster and the Ih -C80 cage were shown to be the most stable configuration for Sc3CH@C80 whereas alternative structures give a smaller bonding energy as well as a smaller energy gap. [source] Isomers of C20: An energy profile IIIJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 3 2004Jennifer I. Chavez Abstract Semiempirical calculations, at the PM3 level provided within the Winmopac v2.0 software package, are used to geometrically optimize and determine the absolute energies (heats of formation) of a variety of C20 isomers that are predicted to exist in and around the ring and cage isomers. Using the optimized Cartesian coordinates for the ring and the cage isomers, a saddle-point calculation was performed. The resulting energy profile, consisting of a series of peaks and valleys, is used as a starting point for the identification and location of fifteen additional isomers of C20 that are predicted to be energetically stable, both via geometry optimizations and force constant analysis. These additional isomers were subsequently determined to lie adjacent to one another on the potential surface and establish a step-wise transformation between the ring and the cage. Transition-state optimization of the Cartesian coordinates at the saddle point between adjacent isomers was performed to quantify the energy of the transition state. The step-wise process from one isomer to another, which extends out over the three-dimensional surface, is predicted to require ,15% less energy than that of the direct, two-dimensional transformation predicted in the bowl-cage profile. However, the net atomic rearrangement for the step-wise process is about four times greater than that of the direct process. Although less in energy, the amount of atomic rearrangement in the step-wise process would make the occurrence of such a route prohibitive. Utilizing the direct distance separating the three primary isomers (ring, bowl, cage), the method of triangulation is performed to quantitatively position other C20 structures on the potential surface, relative to the ring, bowl, and cage isomers. © 2003 Wiley Periodicals, Inc. J Comput Chem 25: 322,327, 2004 [source] Isomers of C20: An energy profile IIJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 11 2003Kyle A. Beran Abstract Semi-empirical calculations, at the PM3 level provided within the Winmopac v2.0 software package, are used to geometrically optimize and determine the absolute energies (heats of formation) of a variety of C20 isomers that are predicted to exist in and around the bowl and cage isomers. Using the optimized Cartesian coordinates for the bowl and the cage isomers, a saddle-point calculation was performed. The output file generated, containing energy, distance, and geometry information, is then organized into a graphical format. The resulting graph, which plots the energy of the 20-atom system as a function of the distance from the geometric midpoint, is a two-dimensional energy profile. This profile illustrates an estimation of the contours on the potential energy surface, showing energy minima and maxima that are encountered as the bowl evolves into the cage structure, or vice-versa. To expand the surface into three dimensions, geometry optimizations were performed on the sets of Cartesian coordinates that correspond to energy minima in the bowl-cage profile. Based on these optimizations, eight additional isomers of C20 have been identified and are predicted to be energetically stable. These additional isomers were subsequently subjected to saddle-point calculations in order to identify those isomers that lie adjacent to one another on the three-dimensional surface. Two isomers that are adjacent to each other will exhibit an energy profile that progresses smoothly from the potential well of each isomer up to the saddle point separating them. Consequently, these adjacent pairs of isomers establish a step-wise transformation between the bowl and the cage. This process, which extends out over the three-dimensional surface, is predicted to require less energy than that of the direct, two-dimensional transformation predicted in the bowl-cage profile. © 2003 Wiley Periodicals, Inc. J Comput Chem 24: 1287,1290, 2003 [source] Structure and Stability of (HBNH)n ClustersCHINESE JOURNAL OF CHEMISTRY, Issue 6 2006Hong Wang Abstract Structures and thermodynamic properties of the imidoboranes (HBNH)n (n=1,16) have been investigated theoretically at the B3LYP/6-31G* level of theory. Needle-shaped oligomers that violate the isolated square rule were found to be more stable than cage isomers. The needle-shaped oligomer with n=16 was predicted to be exceptionally stable at low temperature, hexamer and octamer clusters dominated the gas phase at higher temperature. The highest oligomerization degree of the spontaneous cluster fomation has been estimated. It was concluded that generation of the gas phase (HBNH)n clusters with oligomerization degree n,24 was viable, making these species possible intermediates involved in the gas phase generation of BN nanoparticles. [source] | ||||||||||