The emphasis in the program is on highly accurate computations, with extensive treatment of the electron correlation problem through the multireference configuration interaction, coupled cluster and associated methods.

At that moment, Pulay developed the first analytical gradient code called Hartree-Fock (HF),[2][3][4] and Meyer researched his PNO-CEPA (pseudo-natural orbital coupled-electron pair approximation) methods.

[5][6] In 1980, Werner and Meyer developed a new state-averaged, quadratically convergent (MC-SCF) method, which provided geometry optimization for multireference cases.

[8] About four years later (1984), Werner and Knowles developed on a new generation program called CASSCF (complete active space SCF).

This resulted in the quadratically convergent MCSCF/CASSCF code called MULTI,[10][11] which allowed modals to be optimized a weighted energy average of several states, and is capable of treating both completely general configuration expansions.