結合クラスター法
標準的なCCSD法では、
⟨ Ψ 0 | e − ( T ^ 1 + T ^ 2 ) H ^ e ( T ^ 1 + T ^ 2 ) | Ψ 0 ⟩ = E ⟨ Ψ S | e − ( T ^ 1 + T ^ 2 ) H ^ e ( T ^ 1 + T ^ 2 ) | Ψ 0 ⟩ = 0 ⟨ Ψ D | e − ( T ^ 1 + T ^ 2 ) H ^ e ( T ^ 1 + T ^ 2 ) | Ψ 0 ⟩ = 0 {\displaystyle {\begin{aligned}\langle {\Psi _{0}}\vert e^{-({\hat {T}}_{1}+{\hat {T}}_{2})}{\hat {H}}e^{({\hat {T}}_{1}+{\hat {T}}_{2})}\vert {\Psi _{0}}\rangle &=E\\\langle {\Psi _{S}}\vert e^{-({\hat {T}}_{1}+{\hat {T}}_{2})}{\hat {H}}e^{({\hat {T}}_{1}+{\hat {T}}_{2})}\vert {\Psi _{0}}\rangle &=0\\\langle {\Psi _{D}}\vert e^{-({\hat {T}}_{1}+{\hat {T}}_{2})}{\hat {H}}e^{({\hat {T}}_{1}+{\hat {T}}_{2})}\vert {\Psi _{0}}\rangle &=0\end{aligned}}}