Is the FeC cluster linear? Theoretical study of the equilibrium structure and bonding of FeC

Abstract

AbstractAb initio electron correlation methods and density functional theory are used to investigate the structure, bonding, and stability of FeC. Theoretical calculations show that the ground state of the FeC anion strongly depends on the level of theory. The linear 4Σ− state with an open configuration δ2σ1 is predicted to be the ground state of FeC at the coupled‐cluster theory restricted to single, double, and noniterative triple excitations (CCSD[T])//CISD and multireference (MR) second‐order Moller–Plesset (MP2)//CAS self‐consistent field (SCF) levels. Next stable conformations are a C2V ring structure II (4B2) and a C2V structure III (4A2) in which Fe is bonded to one carbon atom of a triangular C3. However, CISD and CCSD//CISD calculations show that the C2V ring structure II and the C2V structure III are more slightly stable than is the linear structure I of FeC. The harmonic vibrational frequencies and relevant vertical electron binding energies are reported. Possible detachment transitions in the photoelectron spectrum of FeC are discussed on the basis of current calculations. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 93: 275–279, 2003