Unitary group adapted state-specific multi-reference coupled cluster theory: Formulation and pilot numerical applications

摘要: We present the formulation and implementation of a spin-free state-specific multi-reference coupled cluster (SSMRCC) theory, realized via unitary group adapted (UGA) approach, using multi-exponential type expansion wave-operator Ω. The operators are defined in terms generators, normal ordered exponential parametrization is utilized for instead pure exponentials. Our Ansatz Ω natural extension spinorbital based Jeziorski-Monkhorst (JM) Ansatz. results terminating series direct term MRCC equations, it uses ordinary Wick algebra to generate working equations straightforward manner. call our as UGA-SSMRCC theory. Just case SSMRCC there redundancies operators, which exploited ensure size-extensivity avoidance intruders suitable sufficiency ...