ffsim.uccsd_generator_unrestricted

ffsim.uccsd_generator_unrestricted(t1, t2)[source]

Unestricted unitary coupled cluster, singles and doubles (UCCSD) generator.

The unrestricted UCCSD generator is

\[T - T^\dagger\]

where \(T\) is the unrestricted CCSD generator (see ccsd_generator_unrestricted()).

Parameters:

  • t1 (tuple[ndarray, ndarray]) – The singles amplitudes. This should be a pair of Numpy arrays, (t1a, t1b), containing the spin-up and spin-down singles amplitudes. t1a should have shape (nocc_a, nvrt_a), where nocc_a is the number of occupied spin-up orbitals and nvrt_a is the number of virtual spin-up orbitals. t1b should have shape (nocc_b, nvrt_b), where nocc_b is the number of occupied spin-down orbitals and nvrt_b is the number of virtual spin-down orbitals.

  • t2 (tuple[ndarray, ndarray, ndarray]) – The doubles amplitudes. This should be a tuple of three of Numpy arrays, (t2aa, t2ab, t2bb).

Return type:

FermionOperator

Returns:

The UCCSD generator.