Electron momentum spectroscopy of metal carbonyls: a reinvestigation of the role of nuclear dynamics

Abstract

The main purpose of this work is to reinvestigate the influence of nuclear dynamics in the electronic ground state of group 6 metal hexacarbonyl compounds [W(CO)6, Cr(CO)6, Mo(CO)6] on electron momentum density profiles obtained from experimental orbital reconstructions employing Electron Momentum Spectroscopy. We call into question the view (Liu et al. in Chem Phys Lett 497:229, 2010) that thermally induced nuclear displacements associated with the first three triply degenerate 1T2g, 1T1u, and 1T2u vibrational eigenmodes can be large enough at or near room temperature (298–310 K) to explain on their own the unexpectedly large electron densities inferred for the frontier orbitals of these compounds at low momenta. In this purpose, we resort to an analysis of populations over these three vibrational eigenmodes, according to a description of vibrational excitations employing Maxwell–Boltzmann statistical thermodynamics. Comparison is made with Born–Oppenheimer Molecular Dynamical (BOMD) simulations over the potential energy surface associated with the electronic ground state. The role of nuclear dynamics in the final ionized state, in the form of Jahn–Teller distortions, is also tentatively investigated.