Jing Li, Ivan Duchemin, Xavier Blase, Valerio Olevano
SciPost Phys. 8, 020 (2020) ·
published 5 February 2020
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Since the '30s the interatomic potential of the beryllium dimer Be$_2$ has
been both an experimental and a theoretical challenge. Calculating the
ground-state correlation energy of Be$_2$ along its dissociation path is a
difficult problem for theory. We present ab initio many-body perturbation
theory calculations of the Be$_2$ interatomic potential using the GW
approximation and the Bethe-Salpeter equation (BSE). The ground-state
correlation energy is calculated by the trace formula with checks against the
adiabatic-connection fluctuation-dissipation theorem formula. We show that
inclusion of GW corrections already improves the energy even at the level of
the random-phase approximation. At the level of the BSE on top of the GW
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.
