H = H o + 1 2 ∑ ∑ i , j ∑ ∑ α α , β β ∂ ∂ 2 ⟨ ⟨ φ φ ⟩ ⟩ ∂ ∂ d i α α ∂ ∂ d j β β | o d i α α d j β β + 1 6 ∑ ∑ i , j , k ∑ ∑ α α , β β , γ γ ∂ ∂ 3 ⟨ ⟨ φ φ ⟩ ⟩ ∂ ∂ d i α α ∂ ∂ d j β β ∂ ∂ d k γ γ | o d i α α d j β β d k γ γ + ⋯ ⋯ = H o + ∑ ∑ i , j ∑ ∑ α α , β β Γ Γ i j , α α β β d i α α d j β β + ∑ ∑ i , j , k ∑ ∑ α α , β β , γ γ Ψ Ψ i j k , α α β β γ γ d i α α d j β β d k γ γ + ⋯ ⋯ ,