MP2Info¶

class MP2Info(qmolecule, threshold=1e-12)[source]¶

Bases: object

A utility class for Moller-Plesset 2nd order (MP2) information

Each double excitation given by [i,a,j,b] has a coefficient computed using

coeff = -(2 * Tiajb - Tibja)/(oe[b] + oe[a] - oe[i] - oe[j])

where oe[] is the orbital energy

and an energy delta given by

e_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

Parameters

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

Methods

`mp2_get_term_info`	With a reduced active space the set of used excitations can be less than allowing all available excitations.
`mp2_terms`	Gets the set of MP2 terms for the molecule taking into account index adjustments due to frozen core and/or other orbital reduction

Attributes

mp2_delta¶

Get the MP2 delta energy correction for the molecule

Returns: The MP2 delta energy
Return type: float

mp2_energy¶

Get the MP2 energy for the molecule

Returns: The MP2 energy
Return type: float