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.