display 2D plot of the molecular-orbital (MO) occupations
MOOccupationsPlot(molecule, method, options)
list of lists; each list has 4 elements, the string of an atom's symbol and atom's x, y, and z coordinates
(optional) method = name/procedure where name is one of 'HartreeFock' (default), 'DensityFunctional','ActiveSpaceCI', 'ActiveSpaceSCF', 'CoupledCluster', 'FullCI','MP2', 'Variational2RDM', 'Parametric2RDM' 'ContractedSchrodinger'
(optional) equation(s) of the form option = value where option is any valid option of the chosen method
MOOccupationsPlot displays the occupations of the molecular orbitals (MOs).
Each occupation is represented by a horizontal line. The most-filled N/2 occupations are colored blue with the rest colored red.
The MO occupations are the eigenvalues of the one-electron reduced density matrix (1-RDM), known as the natural occupations.
The default method is 'HartreeFock' method whose correlation energy is 0.
The result depends upon the chosen molecule, method, and basis set among other options such as charge, spin, and symmetry.
Consider the molecule hydrogen peroxide
mol≔ O, 0.7247, 0, 0, O, −0.7247, 0, 0, H, 0.8233, −0.7, −0.6676,H, −0.8233, −0.6175, 0.7446;
The MO occupations from the Hartree-Fock method are either 1 (oocupied) or 0 (unoccupied)
output≔ MOOccupationsPlotmol, method='HartreeFock';
In contrast, the MO occupations from the parametric 2-RDM method are fractional
output≔ MOOccupationsPlotmol, method='Parametric2RDM';
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