qrunch.chemistry.calculators.trim_configuration_interaction_calculator

Ground state energy calculator using Trimmed Configuration Interaction.

Note that the ground_state_problem may restrict the orbital space.

Classes

Class for performing configuration interaction calculations.

class TrimConfigurationInteractionGroundStateCalculator

Bases: object

Class for performing configuration interaction calculations.

__init__(options: TrimCIOptions | None = None, *, paired_electron_approximation: bool = False) → None

Initialize an instance of TrimConfigurationInteractionGroundStateCalculator.

Parameters:

options (TrimCIOptions | None) – Options to use for the calculation. None results in default options.
paired_electron_approximation (bool) – If True, only paired alpha/beta excitations are used during expansion. This restricts the CI space to determinants reachable via simultaneous identical excitations in both spin channels.

Return type:

None

calculate(problem: ReactionPathProblem) → ReactionPathProblemCalculatorResult

Solve the trimmed configuration interaction (TrimCI) calculation.

Note that the problem may restrict the orbital space.

The Hamiltonian for all geometries is assumed to be real.

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