Ab initio electronic structure methods 2 Calculations 2 Electronic structure 2 Electronic structure theory 2 Excited states 2 Numerical methods 2 coupled cluster theory Chemical elements 1 Cluster analysis 1 Complete basis set limit 1 Computation theory 1 Computational efficiency 1 Configuration-interaction calculations 1 Core-excited state 1 Coupled clusters 1 Electronic ground state 1 Equation of motion coupled clusters 1 Equations of motion 1 Excitation energy 1 Ground state 1 Heavy elements 1 Incremental Strategy 1 Medium-sized molecules 1 Molecules 1 Perturbative treatment 1 Spin orbit coupling 1 Vertical excitation energy 1 Wave function method 1 Wave functions 1 benchmark 1