Reference

From C2 Molecules to Self-Assembled Fullerenes in Quantum Chemical Molecular Dynamics

From C2 Molecules to Self-Assembled Fullerenes in Quantum Chemical Molecular Dynamics. Irle, Stephan; Zheng, Guishan; Elstner, Marcus; Morokuma, Keiji ( Cherry L. Emerson Center for Scientific Computation and Department of Chemistry, Emory University, Atlanta, GA 30322, USA). Nano Letters, 3(12), 1657-1664 (English) 2003 American Chemical Society. CODEN: NALEFD. ISSN: 1530-6984. DOCUMENT TYPE: Journal CA Section: 66 (Surface Chemistry and Colloids) We present for the first time quantum chem. mol. dynamics simulations for the formation of fullerene mols. from ensembles of randomly positioned C2 mols. in a periodic boundary box. 12070-15-4 and 131159-39-2 which are cas registry numbers of chemicals are mentioned. In this investigation, 25 trajectories were run at 2000-3000 K temp., periodically adding batches of more C2 mols. Four trajectories led to spontaneous self-assembly of fullerene mols. within 85 ps through three distinct stages: nucleation of polycyclic structures, growth by ring condensation of attached carbon chains, and cage closure. .

Fullerite additions as a phonon scattering mechanism in p-type Si-20 at

Fullerite additions as a phonon scattering mechanism in p-type Si-20 at.% Ge. Cook, B. A.; Harringa, J. L.; Loughin, S. (Ames Laboratory, Iowa State University, Ames, IA 50011-3020, USA). Materials Science & Engineering, B: Solid-State Materials for Advanced Technology, B41(2), 280-288 (English) 1996 Elsevier. CODEN: MSBTEK. ISSN: 0921-5107. DOCUMENT TYPE: Journal CA Section: 76 (Electric Phenomena) Section cross-reference(s): 52, 69 In expts. to evaluate the possibility of reducing the lattice thermal cond. in Si-Ge alloys through the formation of an inert, intragranular nanophase, a no. of p-type Si-20 at.% Ge alloys, nominally doped with 0.5 at.% B, were prepd. with varying amts. of fullerite, a mixt. of 90% C60 + 10% C70. The fullerite, in the form of a fine black powder with a particle size of 0.7 nm, was shown by XRD to be nearly amorphous. The alloys were synthesized by mech. alloying and the fullerite was added during various stages of prepn. Following consolidation by hot pressing, the compacts are fully dense and homogeneous. Slices of each compact were characterized by the Hall effect at room temp. and also by elec. resistivity, the Seebeck coeff., and thermal diffusivity measurements to 1000°. Addn. of 0.2-0.8% fullerite by a simple mech. blending operation resulted in an overall decrease in the carrier concn. of ￡35% in alloys hot pressed at 1200°, compared with 3.0 ′ 1020 cm-3 for baseline alloys without fullerite addns. Higher hot-pressing temps. 409-21-2 and 131159-39-2 are cas registry numbers of chemicals which are used as reagents here. resulted in increases in both the carrier concn. and carrier mobility. A redn. in thermal cond. of ￡22% compared with std. p-type alloys was obsd. in samples contg. 0.8% addns. A max. integrated av. figure of merit, Z, at 300-1000° of 0.65 ′ 10-3 degree-1 was obtained, corresponding to 0.4% addn. of fullerite, which is 30-35% higher than that of std. p-type Si-Ge alloys doped with 0.25 at.% B prepd. by conventional methods. Larger amts. of fullerite caused a decrease in Z. Observation of selected samples by TEM revealed that the fullerite reacted with Si to form nanophase SiC inclusions. .