Potential energy surfaces for RhCO from DFT calculations

Abstract

AbstractWe present potential energy surfaces for RhCO obtained from density functional theory for two electronic states of RhCO. We have performed local spin‐density calculations including relativistic as well as gradient corrections. The construction of a reasonably accurate atom–atom potential for RhCO is not possible. We were much more successful in constructing the potential energy surfaces by representing the potential as a spherical expansion. The expansion coefficients, which are functions of the distance between the rhodium atom and the carbon monoxide center of mass, can be represented by Lennard‐Jones, Buckingham, or Morse functions, with an error of the fit within 10 kJ/mol. The potential energy surfaces, using Morse functions, predict that the electronic ground state of RhCO is 2Σ+ or 2Δ. This is a linear structure with an equilibrium distance of rhodium to the carbon monoxide center of mass of 0.253 nm. The bonding energy is −184 kJ/mol. Further, Morse functions predict that the first exicted state is 4A′. This is a bent structure (∠RhCO = 14°) with an equilibrium distance of rhodium to the carbon monoxide center of mass of 0.298 nm. The bonding energy of this state is −60 kJ/mol. Both these predictions are in good agreement with the actual density functional calculations. We found 0.250 nm with −205 kJ/mol for 2Σ+ and 0.253 nm with −199 kJ/mol for 2Δ. For 4A′, we found 0.271 nm, ∠RhCO = 30°, with −63 kJ/mol. The larger deviation for 4A′ than for 2Σ+ or 2Δ is a consequence of the fact that the minimum for 4A′ is a very shallow well. © 1994 by John Wiley & Sons, Inc.