A note about the ground state of the hydrogen molecule
  A trial function is presented for the $H_2$ molecule which provides the most accurate (the lowest) Bohr-Oppenheimer ground state energy among few-parametric trial functions (with $\leq 14$ parameters). It includes the electronic correlation term in the form $\sim \exp{(\gamma r_{12})}$ where $\gamma$ is a variational parameter. 
A.V. Turbiner and N.L. Guevara