• In implicit solvation models the solvent can be coarse-grained as a dielectric continuum, of which the electrostatics is described by Poisson or Poisson-Boltzmann equation.
• Polarizable continuum models (PCMs): apparent surface charge self-consistent reaction field models, reducing a 3D volumetric polarization problem into a 2D surface charge problem. C-PCM, COSMO, SS(V)PE/IEF-PCM are available in Q-Chem.
• Q-Chem employs a Switching/Gaussian (SWIG) discretization scheme to implement these PCMs, which resolves the long-standing potential energy surface discontinuity issue.
• Q-Chem uses an iterative conjugate gradient (CG) solver to solve the surface charge equation in order to achieve linear-scaling.
• Isodensity SS(V)PE eliminates the empiricism associated with cavity construction.
• Solvation energy beyond electrostatic interaction:  nonelectrostatic models including SM8, SM12, SMD and CMIRS.
• Nonequilibrium solvation effect in excitation, ionization and emission: the linear-response (LR) and state-specific approaches.
• PCM is supported in post-HF theories like MP2, EOM-CC and ADC, and also available in energy decomposition analysis (ALMO-EDA).

Experimental and calculated solvent shifts at the ADC(2)/ptSS-PCM level of theory with the PTE, PTD, and scaled PTD* approaches.