Bond additivity corrections for quantum chemistry methods

New bond additivity correction (BAC) methods have been developed li,I the G 2 method, BAC-G?, as well as for a hybrid density functional theory (DFT) M oller-Plesset (MP)2 method, BAG-hybrid. These BAC methods use a new form of BAC corrections, involving atomic, molecular, and bond-wise additive terms . These terms enable one to treat positive and negative ions as well as neu trals. The BAC-G2 method reduces errors in the G2 method due to nearest-nei ghbor bonds. The parameters within the BAC-G2 method only depend on atom ty pes. Thus the BAC-G2 method can be used to determine the parameters needed by BAG methods involving lower levels of theory, such as BAC-hybrid and BAC -MP4. The BAG-hybrid method is expected to scale well for large molecules. The BAC-hybrid method uses the differences between the DFT and MP2 predicti ons as an indication of the method's accuracy, whereas the BAC-G2 method us es its internal methods (G1 and G2MP2) to accomplish this. A statistical an alysis of the error in each of the methods is presented on the basis of cal culations performed for large sets (more than 120) of molecules.