Local approach study of electron correlation effects in the Hubbard model

A variational method which corrects the one-electron ground state locally is applied to study electron correlation effects in the Hubbard model. A two-site cluster approximation is used to calculate the ground state energy functional. For the linear chain and for number of electrons per site up to 0.6, the approximation yields more than 80% of the exact results of Lieb and Wu for the ground state energy. Results for higher dimensional systems are also presented.