Ground and excited state geometries via Mukherjee's multireference coupled-cluster method

► We present a benchmark study of Mukherjee's multireference coupled-cluster method. ► We determine molecular equilibrium structures and adiabatic excitation energies. ► Molecules as large as naphthalene are investigated using analytic gradients. ► We compare the results to those obtained using other coupled-cluster methods. ► The size of the active space is shown to play a crucial role.