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Semiempirical Quantum Mechanics
===============================
For semiempirical quantum mechanics (SQM) engines to fit the AtomicInput/Result schema the following convention is used:
- Method: The unique method name (PM7 or GFN2-xTB) including the parametrisation information is provided, no basis is needed
As for quantum mechanical methods a minimal Molecule object is sufficient as input.
.. note::
Semiemprical engines might not handle the concept of ghost atoms correctly, check carefully how the used engine handles ghost atoms.
To be sure remove ghost atoms from input to semiempirical engines beforehand.
Example
-------
For example, running a calculation with the GFN2-xTB method using the ``xtb`` engine would work like any other QM engine with
.. code:: python
>>> import qcelemental as qcel
>>> mol = qcel.models.Molecule(
... symbols=["O", "H", "H"],
... geometry=[
... [ 0.00000000000000, 0.00000000000000,-0.73578586109551],
... [ 1.44183152868459, 0.00000000000000, 0.36789293054775],
... [-1.44183152868459, 0.00000000000000, 0.36789293054775],
... ],
... )
...
>>> model = qcel.models.AtomicInput(
... molecule=mol,
... driver="energy",
... model={"method": "GFN2-xTB"},
... )
...
>>> import qcengine as qcng
>>> ret = qcng.compute(model, "xtb")
>>> ret.return_result
-5.070451354836705
MOPAC
-----
The following semiempirical Hamiltonians are supported with the MOPAC engine.
============= ===========
Method Basis
============= ===========
mndo None
am1 None
pm3 None
rm1 None
mndod None
pm6 None
pm6-d3 None
pm6-dh+ None
pm6-dh2 None
pm6-dh2x None
pm6-d3h4 None
pm6-3dh4x None
pm7 None
pm7-ts None
============= ===========
xtb
---
The following extended tight binding Hamiltonians are available with the ``xtb`` engine.
=========== ======== ==============================
Method Basis Reference
=========== ======== ==============================
GFN2-xTB None 10.1021/acs.jctc.8b01176
GFN1-xTB None 10.1021/acs.jctc.7b00118
GFN0-xTB None 10.26434/chemrxiv.8326202.v1
=========== ======== ==============================
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