Semiempirical Quantum-Chemical Methods with Orthogonalization and Dispersion Corrections

Abstract

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.