Potential Energy Surface of Group 11 Trimers (Cu, Ag, Au): Bond Angle Isomerism in Au3

J Phys Chem A. 2019 Feb 14;123(6):1198-1207. doi: 10.1021/acs.jpca.8b11219. Epub 2019 Feb 5.

Abstract

Potential energy surfaces for the group 11 trimers were generated at various levels of coupled-cluster theory to examine the effects of Jahn-Teller distortions. Our calculations show that the lowest-energy conformer for Cu3, Ag3, and Au3 is the 2B2 (∼65° isomer) without spin-orbit corrections. Spin-orbit corrections have negligible contributions to the relative energies for the angle dependence of the potential energy surfaces for Cu3 and Ag3. The inclusion of spin-orbit corrections for Au3 makes the 2B2 (∼65°) and 2A1 (∼55°) states approximately degenerate. A novel 2B2 isomer of Au3 at an obtuse angle of ∼125° was also characterized, providing evidence for bond angle isomerism on the same 2B2 potential energy surface. Spin-orbit corrections increase the barrier height between the 2B2 (65°) and 2B2 (125°) bond angle isomers of Au3. The calculated symmetric stretch vibrational frequencies are in good agreement with the available experimental values. All frequencies calculated for the Au3 2B2 (∼125°) state are real, and there is at least one bound bending vibration for this state. Jahn-Teller parameters are also derived for each trimer.