Implicit solvation model can be added to your calculation by using VASPsol tool for VASP. There you can find instructions how to compile VASP with the tool and a couple of example how to use it.

• Do a vacuum calculation for your system first and save the wavefunction file WAVECAR by specifying LWAVE = .TRUE. in the INCAR file.

• Start the solvation calculation from the vacuum WAVECAR, specify ISTART = 1 in the INCAR file.

• The solvation parameters are read from the INCAR file.
  1. LSOL = .TRUE. # switch on the mode for implicit solvent
  2. EB_k = N # relative permittivity of a solvent. Default value is 78.4 for water
  3. Additional parameters:
     1. LRHOB = .TRUE. # writes the bound charge density in the CHGCAR format into RHOB file
     2. LAMBDA_D_K # the Debye length in Angstroms for using the linearized Poisson-Boltzmann model(electrolyte model)
     3. TAU # surface tension parameter

• ENCUT parameter should be high enough: 600 eV (for transition metal oxides) or more. PREC = .Accurate.

• Use the all-electron potentials for H, He, Li and Be

 !------------------------------------------------------------------------
 WARNING: 
 Use all-electron pseudopotential or set CORE_C explicitly 
 for atomic-species with atomic number less than or equal to 4.
 Problem species ATOMIC NUMBER, SYMBOL & VALENCE :           3 Li
   1.00000000000000     
 I HOPE YOU KNOW WHAT YOU ARE DOING !
 !------------------------------------------------------------------------

• NSW = None
• LDIPOL = .FALSE.