Abstract: The multi-electron configurational functions in complete active space (CAS) are classified and characterized by weight vectors (occupation numbers of orbitals). Each configuration has a given weight vector. Configuration space invariant under molecular point group is called equivalent weight space. The Slater determinants are basis functions in each equivalent weight space. The new concepts of symmetrization operators, character Slater bases, character matrices and character configuration functions, and general generation methods of symmetrization function (eigenfunction of S₂ and irreducible representation of molecular point group) are proposed. According to this scheme, the full configurational functions are a sum of these functions obtained by operating the symmetrization operator to character configuration functions, therefore, the physical factors and geometric factors in full configuration functions are completely separated and redundant variance parameters are removed due to symmetry adaptation. The character Slater bases are one-one correspondence with equivalent VBstructure and have a define chemical significance. This method might play an important role in the CItheory and calculations.

Key words: CI method, Complete Active Space, Slater Determinant, Character wave function, UGA and VB method