While n-pentane (n=5) and n-heptane (n=7) are converged, n-hexane may lie at a specific size where the electronic structure or self-consistent field (SCF) calculations fail to stabilize. This issue can arise from either strong oscillation in SCF iterations, or the presence of near-degenerate states, making convergence more challenging for the given methods. For n-hexane, the combination of its molecular symmetry and specific electronic interactions likely caused oscillations in SCF iterations for PBE and TPSS methods. This resulted in unconvergence, whereas n-pentane and n-heptane, with less symmetrical structures, converged successfully. Additionally, near-degenerate states are states in a quantum mechanical system that are close to being degenerate, meaning they have closely spaced electronic energy levels. It makes convergence difficult for DFT methods like PBE and TPSS, which assume a single-reference ground state. Such situations can be overcome by applying the density-functional toolkit, DFTK which explores the convergence behavior of SCF algorithms, emphasizing the impact of mixing parameters and preconditioners on systems with challenging convergence properties . This method is capable of handling cases with degenerate or near-degenerate orbitals where SCF methods might struggle to converge.