Ground-state correlation energy of beryllium dimer by the Bethe-Salpeter equation

Jing Li, Ivan Duchemin, Xavier Blase, Valerio Olevano
2020 SciPost Physics  
Since the '30s the interatomic potential of the beryllium dimer Be_22 has been both an experimental and a theoretical challenge. Calculating the ground-state correlation energy of Be_22 along its dissociation path is a difficult problem for theory. We present ab initio many-body perturbation theory calculations of the Be_22 interatomic potential using the GWGW approximation and the Bethe-Salpeter equation (BSE). The ground-state correlation energy is calculated by the trace formula with checks
more » ... ormula with checks against the adiabatic-connection fluctuation-dissipation theorem formula. We show that inclusion of GWGW corrections already improves the energy even at the level of the random-phase approximation. At the level of the BSE on top of the GWGW approximation, our calculation is in surprising agreement with the most accurate theories and with experiment. It even reproduces an experimentally observed flattening of the interatomic potential due to a delicate correlations balance from a competition between covalent and van der Waals bonding.
doi:10.21468/scipostphys.8.2.020 fatcat:upgpcipvmrhsvdwnzbitwqjzze