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Register a new userMagnetism of Fullerene C60 Compared with Graphene Molecule by DFT Calculation, Laboratory Experiment and Astronomical Observation
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Magnetism of fullerene C60 was studied by three methods of the density functional theory (DFT) calculation, laboratory experiment and astronomical observation. DFT revealed that the most stable spin state was non-magnetic one of Sz=0/2. This is contrary to our recent study on void induced graphene molecules of C23 and C53 to be magnetic one of Sz=2/2. Two graphene molecules combined model suggested that two up-spin at every carbon pentagon ring may cancel each other to bring Sz=0/2. Similar cancelation may occur on C60. Molecular vibrational infrared spectrum of C60 show four major bands, which coincide with gas-phase laboratory experiment, also with astronomically observed one of carbon rich planetary nebula Tc1 and Lin49. However, there remain many unidentified bands on astronomical one. We supposed multiple voids on graphene sheet, which may create both C60 and complex graphene molecules. It was revealed that spectrum of two voids induced graphene molecule coincident well with major astronomical bands. Simple sum of C60 and graphene molecules could successfully reproduce astronomical bands in detail.
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It had been understood that astronomically observed infrared spectrum of carbon rich planetary nebula as like Tc 1 and Lin 49 comes from fullerene (C60). Also, it is well known that graphene is a raw material for synthesizing fullerene. This study seeks some capability of graphene based on the quantum-chemical DFT calculation. It was demonstrated that graphene plays major role rather than fullerene. We applied two astrophysical conditions, which are void creation by high speed proton and photo-ionization by the central star. Model molecule was ionized void-graphene (C23) having one carbon pentagon combined with hexagons. By molecular vibrational analysis, we could reproduce six major bands from 6 to 9 micrometer, large peak at 12.8, and largest peak at 19.0. Also, many minor bands could be reproduced from 6 to 38 micrometer. Also, deeply void induced molecules (C22) and (C21) could support observed bands.
We report on extended investigation of the thermal transport and acoustical properties on hard carbon samples obtained by pressurization of C60 fullerene. Structural investigations performed by different techniques on the same samples indicate a very inhomogeneous structure at different scales, based on fractal-like amorphous clusters on the micrometer to submillimetre scale, which act as strong acoustic scatterers, and scarce microcrystallites on the nanometer scale. Ultrasonic experiments show a rapid increase in the attenuation with frequency, corresponding to a decrease in the localization length for vibrations. The data give evidence for a crossover from extended phonon excitations to localized fracton excitations. The thermal conductivity is characterized by a monotonous increase versus temperature, power law T^(1.4), for T ranging from 0.1 to 10 K, without any well-defined plateau, and a strictly linear-in-T variation between 20 and 300K. The latter has to be related to the linear-in-T decrease of the sound velocity between 4 and 100 K, both linear regimes being characteristic of disordered or generally aperiodic structures, which can be analysed by the phonon-fracton hopping model developed for fractal and amorphous structures.
It is demonstrated that in fullerene C70 which can be considered as a deformed fullerene C60 in some sense there is a withdrawal of an electrodynamical forbiddance of a strong quadrupole light-molecule interaction which is realized in the fullerene C60. This situation occurs because of the reduction of symmetry of C60 from the icosahedral symmetry group Yh to the group D5h. The withdrawal results in appearance of the lines in the SERS spectra of C70 which are forbidden in usual Raman scattering and are allowed in infrared absorption while such lines are forbidden in the SERS spectrum of the fullerene C60 due to the electrodynamical forbiddance. The measured SERS spectra of C70 demonstrates existence of such lines that strongly confirms our ideas about the dipole quadrupole SERS mechanism.
Force and conductance were simultaneously measured during the formation of Cu-C60 and C60-C60 contacts using a combined cryogenic scanning tunneling and atomic force microscope. The contact geometry was controlled with submolecular resolution. The maximal attractive forces measured for the two types of junctions were found to differ significantly. We show that the previously reported values of the contact conductance correspond to the junction being under maximal tensile stress.
We report on the detection of hydromagnesium isocyanide, HMgNC, in the laboratory and in the carbon rich evolved star IRC+10216. The J=1-0 and J=2-1 lines were observed in our microwave laboratory equipment in Valladolid with a spectral accuracy of 3,KHz. The hyperfine structure produced by the Nitrogen atom was resolved for both transitions. The derived rotational constants from the laboratory data are $B_0$=5481.4333(6),MHz, $D_0$=2.90(8),KHz, and $eQq(N)$=-2.200(2),MHz. The predicted frequencies for the rotational transitions of HMgNC in the millimeter domain have an accuracy of 0.2-0.7,MHz. Four rotational lines of this species, J=8-7, J=10-9, J=12-11 and J=13-12, have been detected towards IRC+10216. The differences between observed and calculated frequencies are $<$0.5,MHz. The rotational constants derived from space frequencies are $B_0$=5481.49(3),MHz and $D_0$=3.2(1),KHz, i.e., identical to the laboratory ones. A merged fit to the laboratory and space frequencies provides $B_0$=5481.4336(4),MHz and $D_0$=2.94(5),KHz. We have derived a column density for HMgNC of (6$pm$2)$times10^{11}$,cm$^{-2}$. From the observed line profiles the molecule have to be produced produced in the layer where other metal-isocyanides have been already found in this source. The abundance ratio between MgNC and its hydrogenated variety, HMgNC, is $simeq$20.
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