The block-localized wavefunction method and its application

The block - localized wavefunction(BLW)method, which can turn off the elect ron delocalization in molecules, is introduced. To construct the wave funct ion for a strictly localized structure (or a diabatic state), all electrons and primitive orbitals are partitioned into several subspaces, and each mo lecular orbital is expanded in only one subspace. While the molecular orbit als belonging to the same subspace are imposed to be orthogonal, those belo nging to different subspaces are free to overlap. Similar to Hartree - Fock wave function, BLW is also expressed with a Slater determinant. The energy difference between HF wave function and BLW is the stabilization energy du e to the intramolecular electron delocalization or the intermolecular charg e - transfer effect. In this paper, the applicability of the BLW method is demonstrated by analyzing the rotational barrier in butadiene.