Semiempirical Quantum-Chemical Methods with Orthogonalization and Dispersion Corrections

[Image: see text] We present two new semiempirical quantum-chemical methods with orthogonalization and dispersion corrections: ODM2 and ODM3 (ODMx). They employ the same electronic structure model as the OM2 and OM3 (OMx) methods, respectively. In addition, they include Grimme’s dispersion correction D3 with Becke–Johnson damping and three-body corrections E(ABC) for Axilrod–Teller–Muto dispersion interactions as integral parts. Heats of formation are determined by adding explicitly computed zero-point vibrational energy and thermal corrections, in contrast to standard MNDO-type and OMx methods. We report ODMx parameters for hydrogen, carbon, nitrogen, oxygen, and fluorine that are optimized with regard to a wide range of carefully chosen state-of-the-art reference data. Extensive benchmarks show that the ODMx methods generally perform better than the available MNDO-type and OMx methods for ground-state and excited-state properties, while they describe noncovalent interactions with similar accuracy as OMx methods with a posteriori dispersion corrections.