Crystal Field Splittings in Lanthanide Complexes: Inclusion of Correlation Effects beyond Second Order Perturbation...

Area of Science:

• Quantum Chemistry
• Computational Spectroscopy
• Materials Science

Background:

• Conventional ab initio methods for lanthanide complexes neglect dynamical correlation.
• Complete active space second-order perturbation theory (CASPT2) includes dynamical correlation but faces intruder state issues.
• Variational multireference configuration interaction (MRCI) is accurate but computationally prohibitive for large lanthanide complexes.

Purpose of the Study:

• To develop a computationally feasible MRCI method for lanthanide complexes.
• To assess the influence of dynamical correlation beyond second-order perturbation theory.
• To accurately calculate crystal-field splittings and magnetic properties of lanthanide complexes.

Main Methods:

• Quasi-local projected internally contracted MRCI approach.
• Ab initio calculations incorporating spin-orbit coupling.
• Application to lanthanide complexes [Er{N(SiMe3)2}3] and {C(NH2)3}5[Er(CO3)4]·11H2O.

Main Results:

• The developed MRCI method enables accurate calculations for large lanthanide complexes.
• The influence of dynamical correlation beyond second-order perturbation theory was successfully assessed.
• The method provides improved predictions of crystal-field splittings and magnetic properties.

Conclusions:

• The quasi-local projected internally contracted MRCI method offers a viable alternative for studying lanthanide complexes.
• This advancement allows for more accurate theoretical investigations of their electronic and magnetic behaviors.
• The findings pave the way for more precise computational studies in lanthanide chemistry.