Environment

Environment#

CPCM#

The conductor-like polarizable continuum model (CPCM) is implemented in VeloxChem for implicit solvation [TMC05].

A separation is made between equilibrium and non-equilibrium solvation. In the former case, the timescale is such that both nuclear and electronic relaxations take place in the environment, such as in molecular structure optimizations. In the latter case, only electrons are fully equilibrated with the time-dependent solute charge density, such as in UV/vis spectrum simulations.

Python script

Change to examples of structure optimization and UV/vis spectrum and show both types of solvation.

import veloxchem as vlx

xyz_string = """
...
"""

molecule = vlx.Molecule.read_xyz_string(xyz_string)
basis = vlx.MolecularBasis.read(molecule, 'def2-svp')

scf_drv = vlx.ScfRestrictedDriver()
scf_drv.solvation_model = 'cpcm'
scf_drv.cpcm_epsilon = 78.39  # water
scf_drv.filename = 'mol-cpcm'

scf_results = scf_drv.compute(molecule, basis)

Download a Python script type of input file to perform an SCF calculation for ethanol in a water environment.

Text file

@jobs
task: scf
@end

@method settings
basis: def2-svp
xcfun: b3lyp
solvation model: cpcm
cpcm epsilon : 78.39
@end

@molecule
charge: 0
multiplicity: 1
xyz:
...
@end

Download a text format type of input file to perform an SCF calculation for ethanol in a water environment.

SMD#

The Solvation Model based on Density (SMD) is implemented in VeloxChem for implicit solvation [MCT09]. In Veloxchem, the electrostatic contribution is computed using the CPCM model.

Python script

import veloxchem as vlx

xyz_string = """
...
"""

molecule = vlx.Molecule.read_xyz_string(xyz_string)
basis = vlx.MolecularBasis.read(molecule, 'def2-svp')

scf_drv = vlx.ScfRestrictedDriver()
scf_drv.solvation_model = 'smd'
scf_drv.smd_solvent = 'water'
scf_drv.filename = 'mol-smd'

scf_results = scf_drv.compute(molecule, basis)

Download a Python script type of input file to perform an SCF calculation for ethanol in a water environment.

Text file

@jobs
task: scf
@end

@method settings
basis: def2-svp
xcfun: b3lyp
solvation model: smd
smd solvent : water
@end

@molecule
charge: 0
multiplicity: 1
xyz:
...
@end

Download a Python script type of input file to perform an SCF calculation for ethanol in a water environment.

Polarizable embedding#

An explicit representation of the environment is available with the polarizable embedding (PE) model. Molecules in the environment are represented by site charges and polarizabilities. VeloxChem presently supports for the PE model in

  • SCF optimizations

  • linear response calculations

The PE model is invoked in input files by giving the name of the associated potential file.

Python script

import veloxchem as vlx

xyz_string = """
...
"""

molecule = vlx.Molecule.read_xyz_string(xyz_string)
basis = vlx.MolecularBasis.read(molecule, 'def2-svp')

scf_drv = vlx.ScfRestrictedDriver()

scf_drv.potfile = "pe.pot"

scf_results = scf_drv.compute(mol, basis)

Text file

@jobs
task: scf
@end

@method settings
basis: aug-cc-pvdz
potfile: pe.pot
@end

@molecule
charge: 0
multiplicity: 1
xyz:
...
@end

Potential file

The potential file named pe.pot in this example takes the following form.

@environment
units: angstrom
xyz:
O   -0.9957202   0.0160415   1.2422556  water  1
H   -1.4542703  -0.5669741   1.8472817  water  1
H   -0.9377950  -0.4817912   0.4267562  water  1
O   -0.2432343  -1.0198566  -1.1953808  water  2
H    0.4367536  -0.3759433  -0.9973297  water  2
H   -0.5031835  -0.8251492  -2.0957959  water  2
@end

@charges
O  -0.67444408  water
H   0.33722206  water
H   0.33722206  water
@end

@polarizabilities
O       5.73935090    0.00000000    0.00000000    5.73935090    0.00000000    5.73935090  water
H       2.30839051    0.00000000    0.00000000    2.30839051    0.00000000    2.30839051  water
H       2.30839051    0.00000000    0.00000000    2.30839051    0.00000000    2.30839051  water
@end

The polarizability components are listed in the order xx, xy, xz, yy. yz, zz.

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