Implicit Solvent Examples

Water with C-PCM

task: SCF RHF/STO-3G

MOLECULE
  Charge        0
  Multiplicity  1
  Units         Angstrom
END

GEOMETRY
  O   0.000000   0.000000   0.117369
  H   0.756950   0.000000  -0.469476
  H  -0.756950   0.000000  -0.469476
END

SOLVATION
  Model           cpcm
  Dielectric      78.3553
  Surface         swig
  Lebedev         110
END

This runs an RHF/STO-3G energy with C‑PCM water. The default surface is SWIG with 110 Lebedev points per atom.

Water with IEF-PCM (tabulated solvent)

task: SCF RHF/6-31G*

MOLECULE
  Charge        0
  Multiplicity  1
END

GEOMETRY
  O   0.000000   0.000000   0.117369
  H   0.756950   0.000000  -0.469476
  H  -0.756950   0.000000  -0.469476
END

SOLVATION
  Model           iefpcm
  Solvent         water
END

The SOLVATION section activates the solvent. The dielectric constant (78.3553) is loaded automatically from the SMD parameter table for water.

Methanol with SS(V)PE and ISWIG surface

task: SCF RHF/6-31G*

MOLECULE
  Charge        0
  Multiplicity  1
END

GEOMETRY
  C   0.049272   0.074722   0.000000
  O   0.049272   1.509864   0.000000
  H  -0.447572  -0.303266   0.891288
  H  -0.447572  -0.303266  -0.891288
  H   1.089478  -0.252237   0.000000
  H  -0.438081   1.909086  -0.755708
END

SOLVATION
  Model           ssvpe
  Solvent         methanol
  Surface         iswig
  Lebedev         194
END

Uses the ISWIG (erf-based) surface for a smoother cavity, with a finer 194-point Lebedev grid.

SMD for Aqueous Solvation

task: SCF B3LYP/6-31+G**

MOLECULE
  Charge        0
  Multiplicity  1
END

GEOMETRY
  O   0.000000   0.000000   0.117369
  H   0.756950   0.000000  -0.469476
  H  -0.756950   0.000000  -0.469476
END

BASIS
  Library 6-31+G**
END

SOLVATION
  Model           smd
  Solvent         water
  Surface         swig
  Lebedev         110
END

SMD uses IEF-PCM electrostatics with SMD-parametrized radii and adds a density-independent CDS free energy.

Geometry Optimization in Solvent

task: OPT RHF/6-31G*

MOLECULE
  Charge        0
  Multiplicity  1
END

GEOMETRY
  O   0.000000   0.000000   0.117369
  H   0.756950   0.000000  -0.469476
  H  -0.756950   0.000000  -0.469476
END

SOLVATION
  Model           iefpcm
  Solvent         water
END

OPT
  Algorithm  berny
  Coord      tric
  MaxCycle   100
END

Geometry optimizations with solvent recompute the cavity at each step (the cavity is a function of geometry). Analytical gradients include the full PCM contribution.

Frequency Analysis in Solvent

task: FREQ RHF/6-31G*

MOLECULE
  Charge        0
  Multiplicity  1
END

GEOMETRY
  O   0.000000   0.000000   0.117369
  H   0.756950   0.000000  -0.469476
  H  -0.756950   0.000000  -0.469476
END

SOLVATION
  Model           cpcm
  Dielectric      78.3553
  Surface         swig
  Lebedev         110
END

FREQ
  Hessian      analytical
  Temperature  298.15
  Pressure     1.0
END

Harmonic frequencies with implicit solvent. The analytical Hessian includes the PCM curvature (hess_nuc + hess_solver). The electron–cavity integral curvature (hess_qv) is currently approximated; finite-difference Hessians (freq=(numerical)) give the full solvent response at higher computational cost.

ddCOSMO Energy

task: SCF RHF/STO-3G

MOLECULE
  Charge        0
  Multiplicity  1
END

GEOMETRY
  H   0.000000   0.000000   0.000000
  H   0.000000   0.000000   1.400000
END

SOLVATION
  Model           ddcosmo
  Dielectric      78.3553
END

ddCOSMO uses a domain-decomposition solver with spherical-harmonic expansion (lmax = 6 by default). The analytical gradient is available but the analytical Hessian is not yet implemented for ddCOSMO/ddPCM.

Output: Solvent Block

When solvent is active, the output header includes a solvent summary:

  Solvent Settings
  --------------------------------------------------
  Model              : C-PCM
  Solvent            : water
  Dielectric         : 78.3553
  Surface            : SWIG
  Lebedev points     : 110
  VDW scale          : 1.000
  Probe radius       : 0.000 Å

Known Limitations