Europium dimer: van der Waals molecule with extremely weak antiferromagnetic spin coupling

摘要

High-level ab initio calculations reveal that the Eu_2 dimer is a van der Waals molecule with extremely weak antiferromagnetic spin coupling. The Heisenberg spin-exchange model, validated by the multireference configuration interaction method, is used to construct the full set of model interaction potentials for the states with the total spin S ranging from 0 to 7 at the coupled cluster level of theory. This model establishes the singlet ~1∑_g~+ state as the ground one of the dimer with the binding energy of 710 cm~(-1), the vibrational frequency of 23 cm~(-1) and the effective spin-coupling constant J estimated approximately -0.3 cm~(-1).