A b i n i t i o study of the ground state surface of Cu3

An ab initio study that includes relativistic effects via first-order perturbation theory and correlation effects using the coupled pair functional formalism is presented for the ground state surface of Cu3. An analogous calculation is presented for the 1Σ+g ground state of Cu2 for calibration. The ground state of Cu3 is found to be a 2B2 state corresponding to a Jahn–Teller distortion (R=4.396 a0, θ=64.5°) of a 2E′ equilateral triangle geometry. This structure is found to lie 59 cm−1 below the 2A1C2v geometry and 280 cm−1 below the D3h equilateral geometry in good agreement with the pseudorotation barrier and Jahn–Teller stabilization energy deduced by Truhlar and Thompson from analysis of the fluorescence spectrum of Rohlfing and Valentini.