Towards an ab initio incremental correlation treatment for metals

Ab initio electron correlation calculations based on quantum chemical methods are successfully applied to a metallic system. As a test system we select one-dimensional Lin rings up to n=62. The correlation energy is determined within an incremental scheme, where the individual energy increments are calculated with local orbitals. The local orbitals are generated by projecting the atomic 2s orbitals onto the occupied Hartree–Fock space. Multi-reference methods are applied to deal with the low-lying excitations in a metal.