Magnetic Moment and Spin-State Transitions in Twisted Graphene Nanostructures

The emergence of magnetic moments and spin-state transitions in the AA-stacking regions of twisted graphene nanoflakes is analyzed by using Density Functional Theory (DFT). Systems of different sizes (C₁₉₂H₄₈, C₃₀₀H₆₀, and C₄₃₂H₇₂) are employed to model some possible stacking angles. Potential Energy Curves (PECs) are computed for different interlayer distances and twist angles, revealing that the triplet ground state appears only in the repulsive region of the PEC, with the transition distance depending on the flake size. The results indicate that interlayer repulsion and twisted angle play significant roles in determining magnetic properties, while spin density analysis confirms that edge effects and AB-region confinement are fundamental to the emergence of magnetic moments in twisted graphene bilayers.