qrunch.chemistry.calculators.coupled_cluster_calculator

Ground state energy calculator using coupled cluster theory.

Note that the ground_state_problem may restrict the orbital space, in which case this is not a standard coupled cluster calculation but a calculation with a truncated orbital space. In case of a restricted orbital space the inactive energy contribution associated with the active space is included in the ground_state_problem.

Classes

CoupledClusterGroundStateCalculator

Class for performing coupled cluster calculations (CCSD or CCSD(T)).

class CoupledClusterGroundStateCalculator

Bases: object

Class for performing coupled cluster calculations (CCSD or CCSD(T)).

__init__(method: Literal['ccsd', 'ccsd_t'] | None = None, options: CoupledClusterGroundStateProblemCalculatorOptions | None = None) → None

Initialize an instance of CoupledClusterGroundStateCalculator.

Parameters:

method (Literal['ccsd', 'ccsd_t'] | None) – Coupled cluster method to use. Default is CCSD.
options (CoupledClusterGroundStateProblemCalculatorOptions | None) – Options to use for the calculation. None results in default options.

Return type:

None

calculate(problem: GroundStateProblem) → GroundStateProblemCalculatorResult

calculate(problem: ReactionPathProblem) → ReactionPathProblemCalculatorResult

Solve the coupled cluster problem.

Note that the ground_state_problem may restrict the orbital space, in which case this is not a standard coupled cluster calculation but a calculation with a truncated orbital space. In case of a restricted orbital space the inactive energy contribution associated with the active space is included in the ground_state_problem.

The Hamiltonian for all geometries is assumed to be real.

Parameters:: problem (RestrictedGroundStateProblem | UnrestrictedGroundStateProblem | RestrictedReactionPathProblem | UnrestrictedReactionPathProblem) – The problem to calculate the ground state energy / energies for.
Return type:: GroundStateProblemCalculatorResult | ReactionPathProblemCalculatorResult