An accurate single centered method for molecular calculations, based on the modified configuration interaction method with infinite angular expansions, is introduced. A calculation of the ground state energy of the hydrogen molecular ion in the Born-Oppenheimer approximation is presented as an example yielding an accuracy for the energy of 7 x 10(-8) a.u. which rivals the best multi-centered Gaussian or Slater calculations. Not only is the single-centered calculation simpler than the multi-centered ones but it allows one to introduce rigorously the vibrational-rotational motion of the nuclei. A discussion of the work in progress on the inclusion of nuclear motion using the newer radially uncoupled configuration interaction method is presented.