ORCA 6.1.1 diatomic local spline example

25 own actual RHF/STO-3G H2 single-point calculations, R=0.45..1.65 A by0.05.
The electronic results are a small-basis restricted-HF teaching dataset, not an
accurate experimental dissociation curve. No GPU was used.

Fresh native postprocessing: bash run.sh
Inspect and plot the provided reference: bash analyze.sh
Inspect new postprocessing: bash analyze.sh work

run.sh adopts the 25 provided own existing scientific SCF outputs and reruns
orca_fitpes for H2, D2, and a bohr-coordinate control. It does NOT run25 newSCFs.
One manual SCF input is inputs/H2-single.inp; original inputs and actual outputs
for every bond length are in reference/STO-3G-R/. All native postprocessor
inputs and logs are preserved. No binary, GBW, credential or runtimeUIDrecord
is included in this package.

fitpes header: N_PES N_POINTS IsAng mass1_u mass2_u.
The present one-PES inputs use N_PES=1,N_POINTS=25; IsAng=1 for Angstrom and0
for bohr. Each following row is R E_Hartree. Coordinates and energies must be
interleaved by point; do not put all coordinates before all energies.

Qualified numerical scope: the SPLINE branch minimum, local curvature and
harmonic frequency only. Independent natural-cubic interpolation reproduces
all25 actual samples, the minimum and curvature, and SI reduced-mass frequency.
Native Chebyshev/Morse output is retained raw; it is NOT automatically a
validated alternative or an accurate dissociation energy. Do not use negative
depths/NaNs or unconstrained finite-window extrapolation as physical results.
The harmonic level figure is an analytic illustration from local curvature,
not a new Hessian, anharmonic spectrum or thermochemistry calculation.

ORCA is the official precompiled CPU6.1.1 distribution, with OpenMPI4.1.8
built using GCC13.3. Python uses existing ASE3.29.0 NumPy/SciPy/Matplotlib.
