Surface adsorption of TbL1 and TmL1 on a monolayer of MoSSe: A theoretical study

In this work, we study the surface adsorption of two mononuclear lanthanide complexes, TbL₁ and TmL₁ (with L = C33H33N4O3), on a monolayer of MoSSe. Stable adsorption configurations are examined using a combination of methods, including the Lennard-Jones force field, the PM7 semi-empirical method, and density functional theory. The crystal field splitting of low-lying energy levels is calculated using the complete active space self-consistent field method before and after surface adsorption. The lowest-lying energy levels of both TbL₁ and TmL₁ correspond to a total angular momentum of J = 6. For an isolated TbL₁, the ground state is dominated by m_J = 0, with the first and second excited states being quasi-degenerate. After surface adsorption, this quasi-degeneracy is broken, resulting in a quasi-doublet formed by the ground state and the first excited state. For TmL₁, the ground state and the first excited state are consistently dominated by m_J = ±6, regardless of the presence of the MoSSe substrate. The quasi-doublet of TmL₁ becomes more separated from the higher energy levels after surface adsorption, which is desirable for quantum information applications. Spin-phonon coupling in these systems will be studied in the next step.