Struct CC::Options

Nested Relationships

This struct is a nested type of Class CC.

Struct Documentation

struct Options

Configuration options for CC class.

Public Members

SEQUANT_DESIGNATED_INIT_ONLY
Ansatz ansatz = Ansatz::T

type of CC ansatz. see CC::Ansatz

std::optional<bool> skip_singles = std::nullopt

if true, singles amplitudes are excluded from \( \hat{T} \) and \( \hat{\Lambda} \); if not specified, defaults to true for orbital-optimized ansätze (oT, oU) and false otherwise. Must be true for orbital-optimized ansätze.

bool screen = true

if true, uses Operator level screening before applying WickTheorem. This propagates to all ref_av() calls

bool use_topology = true

if true, uses topological optimizations in WickTheorem

std::optional<size_t> hbar_comm_rank = std::nullopt

maximum order of nested commutators in H̄; must be specified for a unitary ansatz or when the reference differs from the Wick vacuum, since the expansion does not terminate in either case. Otherwise defaults to 4, which is exact for a two-body Hamiltonian.

size_t hbar_singles_comm_rank = 0

maximum order of the additional singles-only similarity transform applied to H̄ using \( \sigma_1 = T_1 - T_1^\dagger \). Zero disables the transform; a positive rank requires a unitary BCH ansatz with singles amplitudes enabled

std::optional<size_t> pertbar_comm_rank = std::nullopt

maximum order of nested commutators in the similarity transformed perturbation operator; must be specified if unitary ansatz is used in perturbed amplitude derivation

HbarExpansion hbar_expansion = HbarExpansion::BCH

choice of H̄ expansion; Bernoulli requires the U ansatz, not merely a unitary one, and ignores screen and use_topology, see hbar()