SMx Continuum Models for Condensed Phases

The SMx continuum models are designed to include condensed-phase effects in classical and quantum mechanical electronic structure calculations and can also be used for calculating geometries and vibrational frequencies in condensed phases. Originally developed for homogeneous liquid solutions, the SMx models have seen substantial application to more complicated condensed phases as well, e.g., the airwater interface, soil, phospholipid membranes, and vapor pressures of crystals as well as liquids. Bulk electrostatics are accounted for via a generalized Born formalism, and other physical contributions to free energies of interaction between a solute and the surrounding condensed phase are modeled by environmentally sensitive atomic surface tensions associated with solute atoms having surface area exposed to the surrounding medium. The underlying framework of the models, including the charge models used for the electrostatics, and some of the models’ most recent extensions are summarized in this report. In addition, selected applications to environmental chemistry problems are presented.