Solvation and Continuum Models
Most chemistry happens in solution, and continuum solvation models capture the effect of solvent by representing it as a polarizable medium surrounding the solute.
Definition
Methods that account for the influence of a solvent on a solute's structure, energetics, and properties, most economically by treating the solvent as a continuous polarizable dielectric.
Scope
Covers the modeling of solvent effects, implicit continuum models such as the polarizable continuum model, COSMO, and the SMD universal solvation model, the partitioning of solvation free energy into electrostatic and non-electrostatic contributions, and the complementary use of explicit and hybrid explicit/implicit treatments.
Core questions
- How does an implicit continuum represent the averaged effect of a solvent?
- How is solvation free energy decomposed into electrostatic and non-electrostatic parts?
- When are explicit solvent molecules needed alongside or instead of a continuum?
- How do solvent effects change reaction energetics and computed properties?
Key theories
- Continuum dielectric solvation
- Represents the solvent as a polarizable dielectric continuum surrounding a molecular cavity, with the solute polarizing the medium and the medium reacting back on the solute.
- Universal solvation models
- Parameterized continuum models such as SMD combine an electrostatic continuum with empirical terms to predict solvation free energies across many solutes and solvents.
Clinical relevance
Solvation models are essential for realistic predictions of acidity, redox potentials, reaction energetics, and solubility in solution, where neglecting the solvent can give qualitatively wrong results.
History
From the Onsager reaction-field idea, continuum solvation matured through the polarizable continuum model developed by Tomasi and coworkers and the COSMO and SMD models, making solution-phase calculations routine.
Key figures
- Jacopo Tomasi
- Benedetta Mennucci
- Christopher Cramer
- Donald Truhlar
Related topics
Seminal works
- tomasi2005
- marenich2009
Frequently asked questions
- When is an implicit solvent model insufficient?
- When specific solute-solvent interactions such as hydrogen bonds matter, an implicit continuum can miss important effects, and explicit solvent molecules or hybrid treatments are needed.
- What does a solvation model add to a gas-phase calculation?
- It supplies the stabilization and structural and energetic changes a solvent imposes, which can substantially alter relative energies, barriers, and properties from their gas-phase values.