Implicit Solvation

If you want to avoid the expensive sampling of explicit solvent molecules around a system, implicit solvation might be a good solution. VASP itself does not have implicit solvation included, but you can do a manual patch with the VASPsol package (see here).

The installation process is well documented on the github page of the authors.

After installing it, only single point energies can be calulated with solvation, no gradients or frequencies!

In order to calculate the solvation energy of a structure, two calculations must be done:

1. Do a usual single point calculation (with high accuracy, etc., see here), and activate LWAVE = .TRUE. (wave function will be written to file WAVECAR)
2. Do a second single point calculation with the same settings as above, but with the following additional keywords:

• ISTART = 1 The orbitals are read in from the WAVECAR file.
• LSOL = .TRUE. Activates the solvation calculation
• EB_k = [value] Relative permittivity of the solvent (e.g., for water: EB_k = 78.4). The value for the desired solvent should be taken from literature.

After doing both calculations, note the final energy of both, the energy difference then is the solvation energy.