Metallic bonding due to correlations: A quantum chemical ab-initio   calculation of the cohesive energy of mercury
  Solid mercury in the rhombohedral structure is unbound within the self-consistent field (Hartree-Fock) approximation. The metallic binding is entirely due to electronic correlations. We determine the cohesive energy of solid mercury within an ab-initio many-body expansion for the correlation part. Electronic correlations in the $5d$ shell contribute about half to the cohesive energy. Relativistic effects are found to be very important. Very good agreement with the experimental value is obtained. 
Beate Paulus and Krzysztof Rosciszewski