Non-empirical molecular orbital studies of the possibility of ferromagnetic ordering in isoelectron-substituted ferrocarbon modifications

Abstract

The vertical singlet-triplet (ST) splitting in the C 3H 6 molecule and C 2BH 6 − and C 2NH 6 + ions has been investigated by means of ab initio calculations. The molecular geometry was either taken as that corresponding to the UHF/6–31G ∗ or UHF/6–31 + G ∗ energy minimum of the triplet configuration (for C 3H 6, C 2BH 6 −, C 2NH 6 +), or was extracted from the ferrocarbon crystal (for C 3H 6). Polarized split-valence basis sets (6–31G ∗, 6–31 + G ∗ and 6–311G ∗∗) and fourth-order Møller-Plesset perturbation theory at the MP4SDTQ level of approximation provides more reliable ST splitting values, than the MP4SDQ level, the latter being the most accurate method used in our previous work. These calculations prove the presence of ferromagnetic ordering within the same quasi-graphite plane of ferrocarbon crystal. The presence of such ordering has been shown within the same quasi-graphite plane upon substitution of sp 3 carbon atoms by ions B −, N + and so on.