A G3 Study of the Structure of Carbon−Nitrogen Nanoclusters

Abstract

Possible structures of the carbon-nitrogen clusters of the form C(m)N(n) (m = 1-4, n = 1-4, m + n = 2-5) were predicted for the neutral, anion, and cation species in the singlet, doublet, and triplet states, whenever appropriate. The calculations were performed at the G3, MP2(fc)/6-311+G*, and B3LYP/6-311+G* levels of theory. Several molecular properties related to the experimental data--such as the electronic energy, equilibrium geometry, binding energy, HOMO-LUMO gap (HLG), and spin contamination <S(2)>--were calculated. In addition the vertical electron attachment, the adiabatic electron affinity, and vertical ionization energy, of the neutral clusters were calculated. Most of the predicted lowest energy structures were linear, whereas bent structures became more stable with the increase of the cluster size and increase of the number of the N atoms. In most of the predicted lowest energy structures, the N atom prefers the terminal position with acetylenic bond. The calculated BE of the predicted clusters increases with the increase of the cluster size for the neutral and cation clusters but decreases with the increase of the cluster size for the anion clusters. The predicted clusters are characterized by high HLG of about 11 eV on the average, with that of the anion clusters is smaller than that for the neutral and cation clusters. It is concluded then that the anion clusters are less stable than the corresponding neutral and cation clusters. Finally, the N(2) loss reaction is treated.

Infrared Photodissociation Spectroscopy of C4N−, C6N− and C8N−

“…Density functional theory (DFT) computations performed by Pascoli and Lavendi then revealed linear (N‐terminated) geometries for all the investigated C 2 n −1 N − ( n= 2–4) and C 2 n N − ( n= 1–3) anions with singlet ( 1 Σ + ) and triplet ( 3 Σ − ) ground states, respectively. More recent theoretical investigations of various C n N m species of different spin state and charge support the results of the DFT computations . For C 4 N − , an electronically closed‐shell singlet 1 A 1 excited state with a branched, kite‐like structure of C 2 v symmetry is predicted +15 kJ mol −1 above the 3 Σ − ground state.…”

“…The long‐range dispersion‐corrected hybrid density functional ωB97X‐D with Dunning's augmented correlation‐consistent triple‐zeta basis set (aug‐cc‐pVTZ) was used for all geometry optimizations and harmonic frequency calculations . The known geometries were considered as starting points for the geometry optimizations (see the Supporting Information for Cartesian coordinates of the minimum‐energy structures) . To account for anharmonic effects and systematic errors on the harmonic force constants, harmonic frequencies were scaled using a method‐dependent scaling factor of 0.957 .…”

“…This might be due to their lower stabilities and smaller dipole moments, complicating their detection by radio astronomy. Theoretical and especially experimental investigations of these systems remain scarce …”

Synthesis and Laser Ablation Mass Spectrometry of Nitrogen-Doped Carbon Materials

“…19,28,29,31,32,38−40 Mogren and co-workers found that the lowest energy structures for the C x N y − clusters with (x + y) ≥ 5 and y ≥ 2 were bent or cyclic. 31 The more abundant clusters we observe in this region coincide with these highly stable cyclic structures.…”

“…Structurally, these clusters are likely linear or bent C x clusters with terminally bound N atoms in the form of CN, that is, they are C (x-1) CN species, as calculated by Mogren et al and seen by others. 28,31,32 In Figure 2b, the signal intensity of the C x N − clusters is diminished, including CN − , but C x N 3 − for x = 2, 3 clusters are observed. The N/C ratio in 2 is 3.6 times higher than the N/C ratio in 1 (Table S1), which presumably accounts for the increased production of multiplynitrogenated clusters upon the ablation of 2.…”