Structural and Magnetic Properties of Gd₃N@C₈₀

Using relativistic and on-site correlation-corrected density functional theory, we have investigated the structural and magnetic properties of recently synthesized Gd₃N@C₈₀. The most stable structure of Gd₃N@C₈₀ has the three magnetic Gd ions pointing to the centers of hexagons in C₈₀. The magnetic ground state of this structure has the three coplanar spins (S = 7/2) offset by 120° angles. At the same time, the state with the highest multiplicity, where all the spins are parallel aligned, is found only about 4.5 meV higher in energy. Therefore, at room temperature, we expect Gd₃N@C₈₀ to be paramagnetic with the spin fluctuating between different multiplicities. As a result, Gd₃N@C₈₀ may exhibit greater proton relaxivity than Gd@C₆₀ and Gd@C₈₂ and serve as a possible candidate for the next generation of commercially available magnetic resonance imaging contrast agents.