Requesting solvation energy
Calculating solvation energy in CASTEP involves performing two separate calculations for an isolated molecule in a supercell: one to simulate the molecule in a vacuum, and another to include the implicit solvation model. The seedname_Solv.castep file reports the solvation energy.
There are certain limitations for solvation energy calculations:
- The system must represent a molecule in a box.
- Symmetry of the system must be P1.
- Calculations must not include spin-polarization.
- Stress calculations are not available.
Use at least a Fine FFT grid Density for solvation calculations; the Precise density is even better. You can specify the FFT grid Density on the
Basis tab of the CASTEP Electronic Options dialog. Also use an increased value of Augmentation density scaling factor, for example 1.5-2.0 instead of the default value of 1.0.
An increased FFT density and energy cutoff can help to eliminate convergence errors for the multigrid solver for electrostatics in a solvent.
To perform a solvation energy calculation
- Choose Modules | CASTEP | Calculation from the menu bar to display the CASTEP Calculation dialog.
- Select the Properties tab.
- Select the Solvation energy checkbox in the list of properties.
- Select the Electronic tab on the CASTEP Calculation dialog. Click More...: to open the CASTEP Electronic Options dialog.
- Select the Solvent tab.
- From the Solvent list, select the solvent to use.
- If you want, you can specify the dielectric constant of the solvent in the Dielectric constant field.
- Keep selection of the Include apolar term and Account for solute-solvent dispersion repulsion checkboxes as a robust default setting.
- If you want, you can specify the surface tension of the solvent in the Solvent surface tension field (in units of N/m).