A utility class for Moller-Plesset 2nd order (MP2) informationEach double excitation given by [i,a,j,b] has a coefficient computed usingcoeff = -(2 * Tiajb - Tibja)/(oe[b] + oe[a] - oe[i] - oe[j])where oe is the orbital energyand an energy delta given bye_delta = coeff * Tiajb
All the computations are done using the molecule orbitals but the indexes used in the excitation information passed in and out are in the block spin orbital numbering as normally used by the chemistry module.
A utility class for MP2 info
qmolecule (QMolecule) – QMolecule from chemistry driver
threshold (float) – Computed coefficients and energy deltas will be set to zero if their value is below this threshold
With a reduced active space the set of used excitations can be less than allowing all available excitations.
Gets the set of MP2 terms for the molecule taking into account index adjustments due to frozen core and/or other orbital reduction
Get the MP2 delta energy correction for the molecule
The MP2 delta energy
Get the MP2 energy for the molecule
The MP2 energy