LDA Predictions of C₂₀ Isomerizations:  Neutral and Charged Species

Abstract

The energies of isomers of C20 including neutral and positively charged ring, fused ring, flake, and fullerene structures have been calculated within the pseudopotential local density approximation (LDA). The objective is to predict the relative energies of the isomers as well as to validate LDA calculations for the carbon system. For C20, high-level coupled-cluster (CCSD(T)) calculations are just possible and are used for comparison. Our most accurate LDA calculations agree with prior calculations quantitatively and remarkably well with extrapolated CCSD(T) calculations. However, various approximations can qualitatively affect the results. For example softening the pseudopotential for carbon can cause the ordering of the isomer stability to reverse even though good agreement with smaller systems is retained. Similar problems can occur if the plane-wave basis is not sufficiently large.

In Situ Laser-Furnace TOF Mass Spectrometry of C36 and the Large-Scale Production by Arc-Discharge

“…Evidently, the Co-UFP and C 60 matrixes play crucial roles in dissipating excess energies upon desorption/ionization. C 60 has been also known as an effective matrix for LD TOF MS. 28 The C 60 molecules, which have a strong absorption at 328 nm close to the N 2 laser wavelength at 337 nm, effectively absorb the laser photons and effectively transfer the corresponding photon energy to C 36 H 6 A MALDI TOF mass spectrum of the purified solid-state C 36 H 6 with a higher laser fluence shows a series of peaks due to the oligomers of C 36 (i.e., C 144 -C 216 ) species and/or their fragments in addition to C 36 H 6 ( Figure 10). It is highly likely that the purified C 36 H 6 forms oligomers or clusters immediately after the removal of solvent CS 2 molecules owing to its very high reactivity.…”

Theoretical study of helium insertion and diffusion in 3C-SiC

“…A softer parametrization was used for carbon [39] to reduce the required number of plane waves. Cluster calculations of carbon have shown that the softer pseudopotential is reliable [40][41][42]. A plane-wave basis with a cutoff of 36 Ry was used for all calculations since previous work on silicon carbide has shown this to be sufficient [39].…”

Most stable structure of fullerene[20] and its novel activity toward addition of alkene: A theoretical study

“…However, the various theoretical calculations present inconsistent results. [14][15][16][17][18][19] Within the molecule orbital ͑MO͒ theory formalism, the I h -symmetric C 20 has the fourfold degenerate highest occupied MO ͑HOMO͒, while only two electrons are populated into these HOMOs. Presumably, such high symmetry will lower due to the Jahn-Teller effect.…”