Substitutional doping of symmetrical small fullerene dimers

Abstract

Magnetic carbon nano-structures have potential applications in the field of spintronics as they exhibit valuable magnetic properties. Symmetrically sized small fullerene dimers are substitutional doped with nitrogen (electron rich) and boron (electron deficient) atoms to visualize the effect on their magnetic properties. Interaction energies suggests that the resultant dimer structures are energetically favorable and hence can be formed experimentally. There is significant change in the total magnetic moment of dimers of the order of 0.5 μ B after the substitution of C atoms with N and B, which can also be seen in the change of density of states. The HOMO-LUMO gaps of spin up and spin down electronic states have finite energy difference which confirm their magnetic behaviour, whereas for non-magnetic doped dimers, the HOMO-LUMO gaps for spin up and down states are degenerate. The optical properties show that the dimers behave as optical semiconductors and are useful in optoelectronic devices. The induced magnetism in these dimers makes them fascinating nanocarbon magnetic materials. K E Y W O R D S magnetism, small fullerenes, substitutional doping 1 | INTRODUCTIONThe discovery of C 60 , among fullerene family, has triggered an interest in the field of carbon nanostructured materials due to their fascinating physical and electronic properties. [1][2][3] An intensive research has been initiated for large and small fullerene derivatives after the large-scale synthesis of C 60 . [1,3,4] Small fullerenes have possible usage in the field of nano-electronics, spin-electronics, molecular devices, superconducting devices, drug delivery, and energy storage owing to their unique physical and chemical properties. [2,[5][6][7][8] C 20 is the smallest fullerene cage that was synthesized using gasphase debromination [9] and was found to be less stable kinetically than higher fullerenes such as C 36 or C 60 due to its strong curvature. [10,11] The carbon cages such as C 32 , C 44 , and C 50 are important because of their large ionization potentials and band gaps. [12] The spectrum of 11.2 μm unidentified infrared band (UIR) indicates that C 24 fullerene cage can be used as a carrier that acts as a useful probe for astrophysical environment. [13] The surface of the fullerenes, depending on its inter-and intra-curvature, determines their stability and electronic properties. The ability of the surface to react with other objects strongly depends on its ability to form chemical bonds. In carbon networks, the substitution of N and B is strongly favorable as they bracket carbon in periodic table. The substitutional doping of N and B in fullerene cage structures leads to increase in their static polarizabilities. [14] The first N doped derivatives of C 60 and C 70 were synthesized using contact-arc vaporization of graphite in the

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