Corrections to the Nonrelativistic Ground Energy of a Helium Atom
  Considering the nuclear motion, the authors give out the nonrelativistic ground energy of a helium atom by using a simple but effective variational wave function with a flexible parameter $k$. Based on this result, the relativistic and radiative corrections to the nonrelativistic Hamiltonian are discussed. The high precision value of the helium ground energy is evaluated to be -2.90338 a.u., and the relative error is 0.00034%. 
Yi-Shi Duan, Yu-Xiao Liu, Li-Jie Zhang