# Energy expressions

AngularMomentumAlgebra.integrate_spinorFunction
integrate_spinor(me)

Perform the spin-angular integration of the matrix element me, leaving only a radial integral multiplied by a spin-angular coefficient. The spin-angular integral is dependent on the specific combination of spin-orbitals and the operator (expressed as a tensor); the default implementation is to leave me as-is, corresponding to a spin-angular integral of unity.

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integrate_spinor(me::OrbitalMatrixElement{2,<:Any,<:CoulombInteraction,<:Any})

Perform the spin-angular integration of the two-electron matrix element me, by first multipole-expanding the Coulomb interaction and then integrating all the resulting terms over the spin-angular coordinates (see multipole_expand).

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integrate_spinor(integral::NBodyTermFactor)

Dummy method that returns integral unchanged, used for all NBodyTermFactors that are not to be multipole-expanded.

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Base.MatrixType
Matrix(op::QuantumOperator,
spin_cfgs::Vector{<:Configuration{<:SpinOrbital}}[, overlaps])

Generate the energy-expression associated with the quantum operator op, in the basis of the spin-configurations spin_cfgs, with an optional set of orbital overlaps, specifying any desired non-orthogonalities. The energy expression is generated in a basis-agnostic way by EnergyExpressions.jl and each term is then integrated over the spin-angular coordinates using integrate_spinor.

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