reconstruct_t2

reconstruct_t2(terms, nocc)

Reconstructs spin-restricted \(t_2\) amplitudes from a double-factorized decomposition.

Computes \(i \sum_k \sum_{pq} Z^{(k)}_{pq} U^{(k)}_{ap} U^{(k)*}_{ip} U^{(k)}_{bq} U^{(k)*}_{jq}\) and slices to the occupied/virtual block [:nocc, :nocc, nocc:, nocc:].

Parameters:

• terms – the list of \((Z, U)\) 2-tuples produced by double_factorized_t2().

• nocc – the number of occupied orbitals.

Returns:

The reconstructed \(t_2\) amplitudes of shape (nocc, nocc, nvrt, nvrt).