PCM/ddX

The current PCM production path is an energy-only reference-SCF workflow using the ddX backend. PCM treats the solvent as a polarizable dielectric continuum around a molecular cavity. OpenQP currently exposes the ddX-backed reference-SCF energy path, which is the first production solvent route and should be kept separate from future state-specific excited-state PCM work. See the References page for continuum-solvation and domain-decomposition ddPCM background.

Input style:

[input]
runtype=energy
method=hf
basis=6-31g*

[scf]
type=rhf
multiplicity=1

[pcm]
enabled=true
backend=ddx
mode=reference_scf
model=ddpcm
epsilon=78.3553

Python style:

from oqp.openqp import OpenQP

job = OpenQP("h2o_pcm", silent=1)
job.molecule(geometry="water", charge=0, multiplicity=1)
job.theory.hf(basis="6-31g*")
job.workflow.pcm(
    enabled=True,
    backend="ddx",
    mode="reference_scf",
    model="ddpcm",
    epsilon=78.3553,
)

mol = job.run()

Runnable input: examples/PCM/H2O_RHF-HF_DDPCM_ENERGY_ISPHER.inp.

Scope

• Supported production mode: backend=ddx, mode=reference_scf, runtype=energy.
• Reference support: RHF and ROHF.
• Python job.workflow.pcm(...) requires an HF/DFT reference-SCF theory. It blocks MRSF-TDDFT, non-ddX backends, non-reference_scf modes, and UHF references before runtime.
• ispher is selected automatically from the basis-shell convention; users do not normally need to set it for PCM/ddX inputs.
• MRSF-TDDFT can use the high-spin ROHF reference density as a reference-SCF PCM baseline.
• PCM gradients, PCM optimizations, Hessians, NACs, and state-specific excited-state PCM are outside this first energy path.