double_factorized_t2

double_factorized_t2(t2_amplitudes, tol, max_terms=None)

Double-factorized decomposition of spin-restricted $t_2$ amplitudes.

Factorizes $t_{ijab}$ (with $i, j$ occupied and $a, b$ virtual) into a list of $(Z, U)$ terms suitable for reconstruction by reconstruct_t2(). The number of terms is truncated to max_terms (default: all).

Parameters

• t2_amplitudes – the $t_2$ amplitudes of shape (nocc, nocc, nvrt, nvrt).
• tol – the tolerance controlling the truncation error of the decomposition.
• max_terms – the maximum number of terms to retain. Defaults to all.

Returns

A list of $(Z, U)$ 2-tuples, where Z is the diagonal Coulomb matrix and U is the orbital rotation.