where 𝐸𝐸 (𝑋𝑋 The wave function for the exciton state (eq 5) can be variationally optimized by using a multiconfiguration self-consistent-field (MC-SCF) approach or configuration interaction such as CIS and nonorthogonal configuration interaction (NOCI), also called mixed molecular orbital and valence bond (MOVB) in WFT. Alternatively, they can be obtained from multistate SCF (MS-SCF) and NOSI methods in MSDFT. NOSI is used in the present study, in which we first determine the locally excited states for monomer X* in the presence of Y in its ground state, and monomer Y* in X, respectively, using the block-localized excitation (BLE) method to variationally optimize Ψ (𝑋𝑋 * •𝑌𝑌)