https://doi.org/10.1007/s100530050362
All electron ab initio investigations of the electronic states of the FeC molecule
1
Department of Applied Chemistry, The Technical University of Denmark,
DTU 375, 2800 Lyngby, Denmark
2
Department of Chemistry, Texas A&M University,
PO Box 300012, College Station, Texas 77843-3012, U.S.A.
Received:
2
October
1998
Revised:
30
March
1999
Published online: 15 September 1999
The low-lying electronic states of the molecule FeC have been investigated
by performing all electron ab initio multi-configuration self-consistent-field
(CASSCF) and multi reference configuration interaction (MRCI) calculations.
The relativistic corrections for the one-electron Darwin contact term and
the relativistic mass-velocity correction have been determined in perturbation
calculations. The electronic structure of the FeC molecule is interpreted
as antiferromagnetic couplings of the localized angular momenta of the ions
and 
resulting in a triple bond in the valence bond sense. The electronic
ground state is confirmed as being 
. The spectroscopic constants for the
ground state and eleven excited states have been derived from the results
of the MRCI calculations. The spectroscopic constants for the ground state
have been determined as 
and 
,
and for the low-lying 
state as 
and 
. The values for the ground state agree well with the available experimental data.
The FeC molecule is polar with charge transfer from Fe to C. The dipole moment has been determined
as 
in the ground state and as 1.51 D in the state. From the
results of the MRCI calculations the dissociation energy, De, is determined
as 2.79 eV, and D0 as 2.74 eV.
PACS: 31.25.Nj – Electron-correlation calculations for diatomic molecules / 31.50.+w – Excited states / 33.15.-e – Properties of molecules and molecular ions
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 1999
