Symmetric 2-body electronic integrals (qiskit_nature.second_q.operators.symmetric_two_body)#

This module provides utilities to deal with symmetry-reduced 2-body electronic integrals.

Container classes#

The classes provided here extend the numpy.ndarray interface and, thus, may be used as such interchangeably.

Nota

Some operations may not be available on the symmetry-reduced space in which case the instance will automatically be unfolded to the full 4-dimensional array. After a successful operation, the original symmetry will be attempted to be restored.

SymmetricTwoBodyIntegrals

An abstract base class providing the interface for symmetry-reduced two-body electronic integral container classes.

S1Integrals

A container for 1-fold symmetric 2-body electronic integrals in chemist ordering.

S4Integrals

A container for 4-fold symmetric 2-body electronic integrals in chemist ordering.

S8Integrals

A container for 8-fold symmetric 2-body electronic integrals in chemist ordering.

Unfolding methods#

These methods can be used to unfold higher symmetries to lower ones.

Nota

This implies that the memory consumption increases.

unfold(eri, *[, validate])

Unfolds an electronic integrals tensor to 1-fold symmetries (4-dimensional).

unfold_s4_to_s1(eri, *[, validate])

Unfolds an 4-fold symmetric tensor to 1-fold symmetries (4-dimensional).

unfold_s8_to_s1(eri, *[, validate])

Unfolds an 8-fold symmetric tensor to 1-fold symmetries (4-dimensional).

unfold_s8_to_s4(eri, *[, validate])

Unfolds an 8-fold symmetric tensor to 4-fold symmetries (2-dimensional).

Folding methods#

These methods can be used to fold lower symmetries to higher ones.

Nota

This implies that the memory consumption decreases.

fold(eri, *[, validate])

Folds an electronic integrals tensor.

fold_s1_to_s4(eri, *[, validate])

Folds a 4-dimensional tensor to 4-fold symmetries (2-dimensional).

fold_s1_to_s8(eri, *[, validate])

Folds a 4-dimensional tensor to 8-fold symmetries (1-dimensional).

fold_s4_to_s8(eri, *[, validate])

Folds a 2-dimensional tensor to 8-fold symmetries (1-dimensional).