Stabilization mechanisms in the Li3+ cluster: A quantum Monte Carlo study of electron delocalization and correlation

We investigate the role of electron delocalization and many-body correlation effects in the energetic stabilization of the Li3+ cluster. Using density functional theory and fixed-node diffusion Monte Carlo calculations, we analyze how symmetry, bond length, and angular distortions influence electron distribution and bonding. In the equilateral triangular (D3h) geometry, molecular orbital symmetry promotes valence electron delocalization, minimizing Coulomb repulsion. At equilibrium, the delocalization enabled by symmetric molecular orbitals dominates the bonding mechanism. However, at extended bond lengths or under angular distortions, the electron correlation becomes increasingly critical to the atomization energy. Our results offer quantitative insights into the stability of few-electron alkali-metal clusters and establish a framework for understanding electronic behavior in low-dimensional metallic systems.