Theoretical investigation of iron carbide, FeC

Abstract

Employing multireference variational methods ͑MRCI͒, we have constructed full potential-energy curves for the ground state (X 3 ⌬) and forty excited states of the diatomic carbide, FeC. For all states we report potential-energy curves, bond lengths, dissociation energies, dipole moments, and certain spectroscopic constants, trying at the same time to get some insight on the bonding mechanisms with the help of Mulliken populations and valence-bond-Lewis diagrams. For the X 3 ⌬ state at the MRCI level of theory, we obtain a dissociation energy D e ϭ86.7 kcal/mol at a bond length r e ϭ1.581 Å. These values compare favorably to the corresponding experimental ones, D e ϭ91.2Ϯ7 ͑upper limit͒ kcal/mol and r e ϭ1.5924 Å. The first excited state ( 1 ⌬) is predicted to be 9.7 kcal/mol above the X-state as compared to an experimental value of 9.786 kcal/mol.

The effect of carbon on the electronic structure of FeNi alloys with a stacking fault

“…This distance is similar to that reported in Fe and Ni carbides, surfaces and the C interaction as an impurity with line defects. The charge transference to Ni and C and the DOS plots agrees with theoretical results in the literature [6,34,[56][57][58][59].…”

“…After optimization, the Fe-C and Ni-C present almost an equivalent distance of 1.80 Å. In a recent paper, Tzelei and Mauridis [56] report that in gas-phase diatomic species Fe-C and Ni-C present bond distances from 1.5 Å to 2.0 Å. Niu et al [57] reported a Fe-C distance near the dislocation core of 1.84 Å using ab-initio calculations. Wu et al [58] report found a distance of 1.80 Å when C is located in a Fe grain boundary.…”

Hydrogen and carbon interaction in a FeNi alloy with a vacancy

“…In a recent work, Tzeli and Mavridis reported that in gas phase diatomic species Fe-C and Ni-C present bond distances from 1.5 Å to 2.0 Å [51]. The Fe-C distance is similar to that reported by Niu et al near a dislocation core in α-Fe of 1.84 Å [52] and by Wu et al on the (111) surface (1.80 Å) [53].…”

Rotational Rest Frequencies for FeN ( X 2 i ) and Revised Spectroscopic Constants for FeC ( X 3 i )

“…Lambda-doubling is caused by perturbations by nearby excited electronic states, in particular 3 P, 1 P, 1 S, and 3 S terms for 3 D ground states. As suggested by ab initio calculations (Shim & Gingerich 1999;Tzeli & Mavridis 2002), such states exist in the FeC manifold, but with the exception of a 3 S Ϫ state, lie quite high in energy (i.e., 115,000 cm Ϫ1 ). Because the magnitude of the lambda-doubling interaction is inversely proportional to the energy differences between the ground and perturbing excited states, the effect of these highlying levels is mitigated.…”