Multireference configuration interaction study of potential energy curves of gold monotelluride (AuTe) and energy levels of Te atom incorporating spin-orbit coupling

The potential energy curves (PECs) for the ground and low-lying excited states of AuTe are calculated using multireference configuration interaction with the Davidson correction, incorporating spin-orbit coupling (SOC). The ground state of AuTe is identified as the Ω = 3/2[(1)²Π_3/2] state. Spectroscopic constants for the ground and low-lying excited states are derived from the computed PECs and generally exhibit excellent agreement with available experimental results. In addition, the experimental energy level ordering of the Te atom, in which the ³P₀ state lies below the ³P₁ state, is successfully reproduced by incorporating both the second-order SOC and dynamic electron correlation effects. The analysis indicates that while second-order SOC contributes to lowering the energy of the ³P₀ state, including the dynamic electron correlation is essential for achieving the correct energy ordering. The spin-orbit (SO) effect in the ground state of AuTe is found to be negligible, resulting from the mutual cancellation of SO contributions from Au and Te atoms, which is rationalized through the natural bond orbital analysis. These results offer valuable insights into the fundamental nature of gold-chalcogen bonding and serve as a benchmark for future experimental and theoretical investigations of AuTe and related systems.