vibeqc.ShortRangeCorrection

class vibeqc.ShortRangeCorrection(name, kind, qscal, rscal, citation)[source]

Bases: object

Canonical short-range bond (SRB) correction of the 3c stack.

HF-3c and B97-3c use genuinely DIFFERENT SRB functional forms, both ported from the authoritative Grimme-lab source (grimme-lab/gcp src/gcp.f90, LGPL-3.0). They are discriminated by kind:

  • kind="hf3c_base" — HF-3c (gcp.f90::basegrad), applied for element pairs with Z = 1..18 only:

    E_SRB = -qscal · Σ_{A<B} (Z_A Z_B)^{3/2}
                · exp(-rscal · r0ab_AB^{0.75} · R_AB)

    with (qscal, rscal) = (0.03, 0.7).

  • kind="b973c_mod" — B97-3c (gcp.f90::srb_egrad2, “modified form derived from the HF-3c SRB potential”, SG Nov-2016), applied for ALL elements:

    E_SRB = -qscal · Σ_{A<B} (Z_A Z_B)^{1/2}
                · exp(-(rscal / r0ab_AB) · R_AB)

    with (qscal, rscal) = (0.08, 10.0).

r0ab_AB is the DFT-D3 ab-initio cut-off radius (bohr) from vibeqc._d3_r0ab (Grimme, Antony, Ehrlich, Krieg, J. Chem. Phys. 132, 154104 (2010)).

The pre-v0.10.4 single form -s·Σ(Z_aZ_b)^0.5·exp(-γ·R^{1/3}) matched NEITHER recipe (audit F1.4): it over-bound HF-3c/H2O SRB roughly 2x (gave ~-52 vs the canonical -22.25 kcal/mol).

Parameters:
name

Human-readable label for the SCF log.

Type:

str

kind

"hf3c_base" or "b973c_mod" — selects the functional form.

Type:

str

qscal, rscal

Per-recipe prefactor and radii-scaling parameter.

Type:

float

citation

Originating publication.

Type:

str

__init__(name, kind, qscal, rscal, citation)
Parameters:
Return type:

None

Methods

__init__(name, kind, qscal, rscal, citation)

evaluate(atomic_numbers, positions)

Evaluate E_SRB (Hartree) for (atomic_numbers, positions in bohr).

Attributes

name

kind

qscal

rscal

citation

name: str
kind: str
qscal: float
rscal: float
citation: str
evaluate(atomic_numbers, positions)[source]

Evaluate E_SRB (Hartree) for (atomic_numbers, positions in bohr). Standalone — no SCF result needed. SRB is binding, so the value is negative for a bound geometry.

Validated against grimme-lab/gcp on the H2O test geometry: HF-3c SRB = -0.035456180 Ha (-22.249 kcal/mol); B97-3c SRB = -0.005713243 Ha (-3.585 kcal/mol).

Return type:

float