Nanostructural magnetism of polymeric fullerene crystals (original) (raw)
Related papers
Testing the magnetism of polymerized fullerene
Physical Review B, 2004
We present band structure calculations of rhombohedral C 60 performed in the local-spin-density approximation. Rhombohedral C 60 (Rh-C 60 ) is a two-dimensional polymer of C 60 with trigonal topology. No magnetic solution exists for Rh-C 60 and energy bands with different spins are found to be identical and not split. The calculated C 2p partial density of states is compared to carbon K-edge x-ray emission and absorption spectra and shows good agreement. It is concluded that the rhombohedral distortion of C 60 itself cannot induce magnetic ordering in the molecular carbon. The result of magnetization measurements performed on the same Rh-C 60 sample corroborates this conclusion.
Structural, electronic, magnetic, and transport properties of carbon-fullerene-based polymers
Oxford Handbooks Online, 2017
This article discusses the structural, electronic, magnetic, and transport properties of carbon-fullerene-based polymers. In particular, it examines the defect-induced ferromagnetism of the C60-based polymers and its analog in the case of non-traditional inorganic materials. It first reviews the computational methods currently used in the literature, highlighting the pros and cons of each one of them. It then considers the defects associated with the ferromagnetism of the C60-based polymers, namely carbon vacancies, the 2 + 2 cycloaddition bonds and impurity atoms, and their effect on the electronic structure. It also evaluates the effect of codoping and goes on to describe the electronic, magnetic and transport properties of the rhombohedral C60-polymer. Finally, it looks at the origin of magnetic coupling among the magnetic moments in the rhombohedral C60-polymer and provides further evidence for the analogy between the magnetism of the rhombohedral C60-polymer and zinc oxide.
Structural and magnetic properties of small symmetrical and asymmetrical sized fullerene dimers
Materials Research Express
Magnetism in carbon nanostructures is of high scientific interest, which could lead to novel magnetic materials. The magnetic properties of symmetrical and asymmetrical sized small fullerene dimers (C n for n≤50) have been investigated using spin polarized density functional theory. The interaction energies depict that small fullerene cages form stable dimer structures and symmetrical sized fullerene dimers are found more stable than asymmetrical sized dimers. The dimerization of fullerene cages in different modes leads to change in their magnetic properties. The non-magnetic fullerene cages become magnetic after formation of dimer (C 20-C 20 , C 24-C 24 , C 32-C 32 , C 40-C 40 , C 20-C 24 , C 40-C 44 and C 44-C 50), whereas the magnetism of magnetic fullerenes is enhanced or lowered after dimerization (C 28-C 28 C 36-C 36 , C 24-C 28 , C 28-C 32 , C 32-C 36 and C 36-C 40). The individual cages of dimer structures show ferromagnetic interactions amongst them and resultant magnetic moment strongly depends on the type of interconnecting bonds. The magnetism may also be explained based on distortion of carbon cages and change in the density of states (DOS) in dimer configuration. The calculations presented show strong possibility of experimental synthesis of small fullerene based magnetic dimers.
Electronic and magnetic properties of small fullerene carbon nanobuds: A DFT study
Materials Research Express
The electronic and magnetic properties of carbon nanobuds have been investigated using density functional theory. The carbon nanobuds are formed by attaching smaller fullerenes (C20, C28, C36 and C40) of variable size with (5,5) ACNT and (5,0) ZCNT. Fullerenes interact strongly with CNT surface having binding energies within the range-0.93eV to-4.06eV. The CC bond lengths near the attachment region increase from the original CC bond lengths. The relative stabilities of the nanobuds are closely related to CC bond lengths and bond angles in cycloaddition reaction. Nanobuds formed by bond cycloaddition are energetically most favorable amongst all cycloadditions. The electronic and magnetic properties of nanobuds depend strongly on electronic properties of its building blocks. The attachment of C20 and C40 on CNTs open up the HOMO-LUMO gaps of nanobuds whereas C28 and C36 results in addition of impurity states near the Fermi level. The total magnetic moment of nanobuds vary from 0.28µB to 4.00µB which depend on the nature of bonding between fullerene and CNTs. The results outline the potential of nanobuds as hybrid carbon nanostructures and how their properties can be tuned with the size and type of fullerene attached.
Electric and magnetic properties of fullerenes
1998
We present fully analytical ab initio calculations of the electric polarizability, the second hyperpolarizability, and the magnetizability of the fullerenes C 70 and C 84 at the self-consistent field level of theory using large basis sets and-in the case of the magnetizability-London atomic orbitals in order to obtain gauge-origin independent results. These calculations are the first ab initio studies of such properties for C 70 and C 84 , and all results are expected to be of near Hartree-Fock limit quality. By comparison with similar results reported earlier for C 60 , valuable insight into the electronic structure of the fullerenes is obtained.
Production and characterization of monomeric C[sub 59]N: A magnetic modification of fullerene
AIP Conference Proceedings, 2001
Solid solutions of C 59 N azafullerene in C 60 with concentrations up to 10" 4 were produced in an electric gas discharge tube and by a heat treatment of (C 59 N) 2 dissolved in pure C 60 . The results on materials produced by the two methods are identical. C 59 N is a stable monomeric substituent molecule in crystalline C 60 and may be heated to temperatures as high as 1300K. The concentration of ESR active neutral C 59 N molecules at ambient temperatures depends on temperature history. CP591, Electronic Properties of Molecular Nanostructures, edited by H. Kuzmany et al.
Transition metal induced magnetism in smaller fullerenes (Cn for n≤ 36)
Nanoscale, 2011
The magnetic properties of 3d transition metals (TM) encapsulated inside smaller fullerenes ranging from C 20 to C 36 have been investigated using spin polarized density functional theory. The TM impurities stabilize asymmetrically at an off-center position for n $ 28. The total magnetic moment (MM) of TM@C n complexes are largely contributed by TMs and a small amount of MM of 0.12-0.50 m B is induced on the cage carbon atoms. The 3d TM atoms interact with C atoms of C 20 and C 28 cage ferromagnetically (FM) except for Ni@C 28 which shows antiferromagnetic (AFM) interaction. The magnetic interactions change from FM to AFM in C 32 cage for Ti, V, Cr and Mn. The MM gets quenched in Ni@C n for n $ 32. The total MM of Mn@C n does not show any change although the nature of magnetic interactions changes from FM to AFM at n ¼ 32. Ti and V are the only TMs which show positive cohesive energy in all fullerenes considered. The smallest fullerene which can encapsulate all 3d TM are C n for n $ 32, consistent with available experimental and theoretical results.
Computational and Theoretical Chemistry, 2012
A density functional study has been performed at B3LYP/6-31G(d) level of theory to investigate the electronic and magnetic properties of the dumbbell-like structures of fullerene dimers with boron-nitride hexagonal bridges C 108 (BN) 3n+6 , and their carbon counterparts C 120+6n , n = 1-10. Interestingly enough, independent of the type and size of hexagonal bridge, the dumbbell-like structures of fullerene dimers represent a short range of negative NICS values (À11.4 to À13.8 ppm) calculated at the cage centers. Moreover, the computed variations of NICS values show that magnetic field decreases by going from the cage centers of fullerene dimers toward the ring centers of hexagonal bridge units. Magnetic field detects different behaviors inside the boron-nitride and carbon hexagonal bridges, an antiaromatic character in the C 120+6n and almost non-aromatic character in the C 108 (BN) 3n+6 compounds. The HOMO-LUMO gap as a function of the number of bridge hexagonal units follows a decreasing zigzag pattern in the C 120+6n while in the C 108 (BN) 3n+6 compounds it shows an upward trend up to C 108 (BN) 12 , and then remains constant until the formation of C 108 (BN) 30. Moreover, binding energies for the C 108 (BN) 3n+6 compounds are always lower than those of the C 120+6n compounds and decrease linearly for both types of the fullerene dimers when the size of the hexagonal bridge increases.
Magnetic Fullerenes inside Single-Wall Carbon Nanotubes
C59N magnetic fullerenes were formed inside single-wall carbon nanotubes by vacuum annealing functionalized C59N molecules encapsulated inside the tubes. A hindered, anisotropic rotation of C59N was deduced from the temperature dependence of the electron spin resonance spectra near room temperature. Shortening of the spin-lattice relaxation time T1 of C59N indicates a reversible charge transfer toward the host nanotubes above ∼350 K. Bound C59N−C60 heterodimers are formed at lower temperatures when C60 is coencapsulated with the functionalized C59N. In the 10–300 K range, T1 of the heterodimer shows a relaxation dominated by the conduction electrons on the nanotubes.
A DFT Study of the Nuclear Magnetic Properties of Fullerenes
2015
The stable configurations, electronic structure and magnetic properties of B16N16, B8C24, Al and P inserted (BC3)8 was studied by performing density functional theory (DFT) calculations of the NMR parameters. The results indicate that B8C24 has semiconductivity property and be effectively modified by inserting groups due to the introduction of certain impurity states within the band gap of the pristine nanostructure, thereby reducing the band gaps. The band gap B8C24 cage is reduced from 2.18 eV to 1.96 (for Al-inserted) and 1.76 eV (for P-inserted), respectively. The calculation of chemical shielding (CS) tensors shown that the B8C24 inserted with Al and P atoms possess a C3v local symmetry with special chemical shifts patterns. Theoretical analyses by molecular orbital under C3v symmetry explain the impurity energy levels and chemical sheilding tensors.The present results are expected to open a way to change the electronic and magnetic properties of studied nanocages, which is he...