qiskit.chemistry.MP2Info

class MP2Info(qmolecule, threshold=1e-12)

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

パラメータ

• 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

__init__(qmolecule, threshold=1e-12)

A utility class for MP2 info

パラメータ

• 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

__init__(qmolecule[, threshold])	A utility class for MP2 info
mp2_get_term_info(excitation_list[, …])	With a reduced active space the set of used excitations can be less than allowing all available excitations.
mp2_terms([freeze_core, orbital_reduction])	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
mp2_energy	Get the MP2 energy for the molecule

property mp2_delta

Get the MP2 delta energy correction for the molecule

戻り値

The MP2 delta energy

戻り値の型

float

property mp2_energy

Get the MP2 energy for the molecule

戻り値

The MP2 energy

戻り値の型

float

mp2_get_term_info(excitation_list, freeze_core=False, orbital_reduction=None)

With a reduced active space the set of used excitations can be less than allowing all available excitations. Given a (sub)set of excitations in the space this will return a list of correlation coefficients and a list of correlation energies ordered as per the excitation list provided.

パラメータ

• excitation_list (list) – A list of excitations for which to get the coeff and e_delta

• freeze_core (bool) – Whether core orbitals are frozen or not

• orbital_reduction (list) – An optional list of ints indicating removed orbitals

戻り値

List of coefficients and list of energy deltas

戻り値の型

Tuple(list, list)

例外

ValueError – Excitation not present in mp2 terms

mp2_terms(freeze_core=False, orbital_reduction=None)

Gets the set of MP2 terms for the molecule taking into account index adjustments due to frozen core and/or other orbital reduction

パラメータ

• freeze_core (bool) – Whether core orbitals are frozen or not

• orbital_reduction (list) – An optional list of ints indicating removed orbitals

戻り値

A dictionary of excitations where the key is a string in the form

from_to_from_to e.g. 0_4_6_10 and the value is a tuple of (coeff, e_delta)

戻り値の型

dict