Low-Energy Electron Scattering from c-C4F8

Electron collision cross-sections of c-C4F8 were investigated at low energies by using the R-matrix method. The static exchange (SE), static exchange with polarization (SEP), and close-coupling (CC) models of the R-matrix method were used for the calculation of the scattering cross-section. The shape resonance was detected with all the models at around 3~4 eV, and a Feshbach resonance was detected with the SEP model at 7.73 eV, in good agreement with the previous theoretical calculation. The resonance detected was also associated with the experimental dissociative electron attachment of c-C4F8, which displayed the resonances at the same energy range. The cross-sections calculated are important for plasma modeling and applications

Boron-Rich Boron Nitride Nanotubes as Highly Selective Adsorbents for Selected Diatomic Air Pollutants: A DFT Study

Boron-rich boron nitride nanotubes (BN-BNNTs), which have boron antisite defects (BN), adsorb gas molecules more favorably as compared to their pristine counterparts because of the localized states of antisites. Using computational chemistry methods, the structural, adsorptive, and electronic properties of selected diatomic air pollutants (CO, NO, and SO) on BN-BNNT (8,0), with a particular focus on the antisites, are investigated. It is found that CO adsorbs on BN with 180° angle (∠BNCO) while NO and SO adsorb with 142° angle (∠BNNO) and 116° angle (∠BNSO), respectively. This difference is ascribed to the repulsive interaction originated from lone pair electrons on N and S. Adsorption energy of CO, NO, and SO molecules dominates over that of O2 and N2 and is independent of their radii of BN-BNNTs. The practical capacity of these pollutant molecules is calculated to be ≈5 mmol g–1 (14 wt%) under ambient conditions. Therefore, our results show that BN-BNNT can be used as a highly selective adsorbent for diatomic air pollutants. BN-BNNT as sensing materials in terms of change in bandgap and work function through the adsorption is also discussed

Electron impact ionization cross section studies of C

The total ionization cross section for C2Fx (x = 1 − 6) and C3Fx (x = 1 − 8) fluorocarbon species are studied with the Binary-Encounter Bethe (BEB) model using various orbital parameters calculated from restricted/unrestricted Hartree-Fock (RHF/UHF) and Density Functional Theory (DFT). All the targets were optimized for their minimal structures and energies with several ab-initio methods with the aug-cc-pVTZ basis set. Among them, the present results with RHF/UHF orbital energies showed good agreement with the experimental results for stable targets C2F6, C2F4, C3F6 and C3F8. The results with the DFT (ωB97X/ωB97X-D) showed a reasonable agreement with the recent calculation of Bull et al. [J.N. Bull, M. Bart, C. Vallance, P.W. Harland, Phys. Rev. A 88, 062710 (2013)] for C2F6, C3F6 and C3F8 targets. The ionization cross section for C2F, C2F2, C2F3, C3F, C3F2, C3F3, C3F4, C3F5 and C3F7 were computed for the first time in the present study. We have also computed the vertical ionization potentials and polarizability for all the targets and compared them with other experimental and theoretical values. A good agreement is found between the present and the previous results. The calculated polarizability in turn is used to study the correlation with maximum ionization cross section and in general a good correlation is found among them, confirming the consistency and reliability of the present data. The cross section data reported in this article are very important for plasma modeling especially related to fluorocarbon plasmas

Low energy cross sections for electron scattering from tetrafluoroallene

We report elastic, total, excitation, differential and momentum-transfer cross sections for scattering of low-energy electrons by tetrafluoroallene (C3F4) using the close-coupling (CC) approximation in the R-matrix method with Quantemol-N. We have tested various target models initially to check for the convergence of the result and the final results are provided with the best target model. We have detected shape resonances of symmetry 2E(2B1,2B2) at 3.08 eV and 3.71 eV with a close-coupling and static exchange models which is seen as a sharp feature in the elastic and momentum transfer cross sections. We also detected other resonances of symmetry 2E at 11.26 eV and of symmetry 2A2 at 11.12 eV below the ionization threshold of the target respectively. The present elastic and total cross sections are compared with the elastic and total cross sections of allene (C3H4), propene (C3H6) and hexafluoropropene (C3F6) as there were no results available for C3F4. The effect of fluorination is clearly seen with the shape resonance for C3F4 getting slightly shifted to higher energies compared to allene. Finally, we also report the ionization cross section calculated using the Binary-Encounter Bethe (BEB) method. The present calculation is a maiden attempt to find cross sections for C3F4 molecule which could be useful for fluorocarbon plasma modeling

Low-Energy Electron Scattering from <i>c</i>-C₄F₈

Electron collision cross-sections of c-C4F8 were investigated at low energies by using the R-matrix method. The static exchange (SE), static exchange with polarization (SEP), and close-coupling (CC) models of the R-matrix method were used for the calculation of the scattering cross-section. The shape resonance was detected with all the models at around 3~4 eV, and a Feshbach resonance was detected with the SEP model at 7.73 eV, in good agreement with the previous theoretical calculation. The resonance detected was also associated with the experimental dissociative electron attachment of c-C4F8, which displayed the resonances at the same energy range. The cross-sections calculated are important for plasma modeling and applications

Electron Impact Cross Sections and Transport Studies of C₃F₆O

Electron impact scattering from C3F6O is studied in this work. The R-matrix method was used for the calculations of elastic, momentum transfer, and excitation cross sections. The attachment cross section was obtained through a parametric estimator based on the R-matrix outputs. The Binary-Encounter-Bethe (BEB) method was used for computing the ionization cross section. The obtained cross section set was used for the transport studies using the BOLSIG+ code, which is a two-term Boltzmann equation solver. The present calculation was performed for steady-state Townsend experimental conditions for E/N, covering a range of 100–1000 Td. The critical dielectric strength of pure C3F6O was found to be 475 Td, which is much greater than that of SF6 (355 Td). The effect of the addition of different buffer gases, such as CO2, N2, and O2, was also examined. For the C3F6O–CO2, C3F6O–N2, and C3F6O–O2 mixtures with 65%, 55%, and 60% C3F6O, respectively, the critical dielectric strength was determined to be essentially the same as that of pure SF6. The presence of synergism was confirmed for these gas mixtures. We further derived the Paschen curve using a fitting method with the transport parameters as the basic inputs. The minimum breakdown voltage of C3F6O accounted for only 55% of that of SF6. The buffer gas mixture improved the condition; however, the performance of CO2 and O2 mixtures was not satisfactory. The addition of N2 as the buffer gas significantly improved the breakdown property of the gas. The mixture of ≥99% of N2 or ≤1% of C3F6O gave a better breakdown characteristic than SF6. Any proportion ≥90% of N2 or ≤10% of C3F6O was suitable in the higher pressure ranges. The present work demonstrates the potential of C3F6O as a substitute gas for SF6 with a negligible environmental threat