Helium computational strategies

Molecular quantum chemistry and quantum mechanical simulation of solids have followed substantially independent paths and strategies for many years, with almost no reciprocal influence. In the implementation of computational schemes and formalisms, they started from different elementary models either the hydrogen or helium atom like, for example, the parameterization of a correlation functional based on accurate He atom calculations by Colle and Salvetti, or the electron gas, which is the reference system of the local density approximation "" (LDA) to density functional theory (DFT). Moreover, if we compare the simplest real crystals, like lithium metal or sodium chloride, with the smallest molecule, H2, the much greater complexity of the solid system is... 

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