From Cyclic Nanorings to Single-Walled Carbon Nanotubes: Disclosing the Evolution of their Electronic Structure with the Help of Theoretical Methods

Guardiola, Andrés Pérez; Ortiz, Ricardo; Sandoval‐Salinas, María Eugenia; Fernández-Rossier, J.; Casanova, David; Jimenez, Angel Jose Perez; Sancho-García, Juan-Carlos

doi:10.26434/chemrxiv.7228646

Cited by 6 publications

(7 citation statements)

References 27 publications

(5 reference statements)

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“…For the 8MC compound we observe a delocalization of the FOD density on the nonbridging C atoms, resembling the results found for other systems with cyclic topologies as cyclacenes (i.e. cyclic oligoacenes91 ).Radical(oid) indices.In order to get a deeper insight into the radical nature of these compounds, in the following we explore them by means of their {y i } indices.Table2presents the y 0 , y 1 , y 2 , and y 3 values for all the systems studied at the FT-TPSS level. The Blatter-like diradicals exhibit nearly ideal diradical character, with y 0 ≃ 1.0 and y i>0 ≃ 0 for the low and high-spin T 0 states.Note that this is in agreement with the smaller N F OD values discussed in the previous section for the HS state of these two systems.…”

supporting

confidence: 81%

Investigating the (Poly)Radicaloid Nature of Real-World Organic Compounds with DFT-Based Methods

et al. 2020

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Recent advances in the synthesis of stable organic (open-shell) polyradicaloids have opened their application as active compounds for emerging technologies. These systems typically exhibit small energy differences between states with different spin multiplicities, which are intrinsically difficult to calculate by theoretical methods. We thus apply here some DFT-based variants (FT-DFT, SF-DFT, and SF-TDDFT) on a test set of large and real-world molecules, as test systems for which such energy differences are experimentally available, also comparing systematically with RAS-SF results to infer if shortcomings of previous DFT applications are corrected. Additionally, we explore the spin-spin contribution to the ZFS tensor, of high interest for EPR spectroscopy, and derive the spatial extent of the corresponding (photoexcited) triplet state.

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confidence: 81%

Investigating the (Poly)Radicaloid Nature of Real-World Organic Compounds with DFT-Based Methods

et al. 2020

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“…We find three Wannier orbitals associated to the 3 narrow bands of figure 5a. The ones corresponding to the first valence and conduction bands are localized in the top and bottom rings of the molecule, at the π orbitals of the hydrogenated carbon atoms, as expected from our previous work for the molecular phase 24 . The one corresponding to the higher energy band has a σ character and a smaller bandwidth thereby, on account of the smaller intermolecular hopping.…”

Section: Energy Bandssupporting

confidence: 80%

“…The electronic properties of [n]CC's depend on the parity of n, showing an odd-even pattern [21][22][23] . This is confirmed at several levels of theory, where a simple oneorbital per atom tight-binding model yields two zero energy states for [even]CC's and four states split in two pairs for [odd]CC's 24 . This provides a simple picture to understand the di/tetraradical character obtained by more sophisticated calculations 25 .…”

Section: Introductionmentioning

confidence: 54%

Frustrated magnetic interactions in a cyclacene crystal

Ortíz¹,

Sancho‐García²,

Fernández-Rossier³

2021

Preprint

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We study the emergence of magnetism and its interplay with structural properties in a two dimensional molecular crystal of cyclacenes, using density functional theory (DFT). Isolated cyclacenes with an even number of fused benzenes host two unpaired electrons in two topological protected zero modes, at the top and bottom carbon rings that form the molecule. We show that, in the gas phase, electron repulsion promotes an open-shell singlet with strong intramolecular antiferromagnetic exchange. We consider a closed packing triangular lattice crystal phase and we find a strong dependence of the band structure and magnetic interactions on the rotation angle of the cyclacenes with respect to the crystal lattice vectors. The orientational ground state maximizes the intermolecular hybridization, yet local moments survive. Intermolecular exchange is computed to be antiferromagnetic, and DFT predicts a broken symmetry 120 • spin phase reflecting the frustration of the intermolecular spin coupling. Thus, the cyclacene crystal realizes a bilayer of two antiferromagnetically coupled S = 1/2 triangular lattices. Our results provide a bottom-up route towards carbon based strongly correlated platforms in two dimensions.

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“…Besides, TAO-DFT has been recently shown to be useful in describing the vibrational spectra of molecules with radical nature 63 . In addition, TAO-DFT and related methods have recently been employed to investigate the electronic properties of several nanosystems with radical nature 64 , 65 , and have also been combined with the linear-scaling divide-and-conquer approach for the study of large systems with strong static correlation effects 66 .…”

Section: Introductionmentioning

confidence: 99%

TAO-DFT investigation of electronic properties of linear and cyclic carbon chains

Seenithurai

Chai

2020

Sci Rep

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it has been challenging to adequately investigate the properties of nanosystems with radical nature using conventional electronic structure methods. We address this challenge by calculating the electronic properties of linear carbon chains (l-cc[n]) and cyclic carbon chains (c-cc[n]) with n = 10-100 carbon atoms, using thermally-assisted-occupation density functional theory (TAO-DFT). For all the cases investigated, l-cc[n]/c-cc[n] are ground-state singlets, and c-cc[n] are energetically more stable than l-cc[n]. the electronic properties of l-cc[n]/c-cc[n] reveal certain oscillation patterns for smaller n, followed by monotonic changes for larger n. For the smaller carbon chains, odd-numbered l-cc[n] are more stable than the adjacent even-numbered ones; c-cc[4m + 2]/c-CC[4m] are more/less stable than the adjacent odd-numbered ones, where m are positive integers. As n increases, l-cc[n]/c-cc[n] possess increasing polyradical nature in their ground states, where the active orbitals are delocalized over the entire length of l-cc[n] or the whole circumference of c-cc[n]. Carbon is the most versatile element in forming various structures. In bulk phase, graphite and diamond, which are well-known materials, have been used for centuries. In nanoforms, fullerenes and graphene have been studied in detail for decades. In general, nanostructures can be classified into three categories: zero-dimensional (0D), one-dimensional (1D), and two-dimensional (2D) nanomaterials. Carbon forms all these nanostructures with unique shapes and properties. Over the past few decades, carbon nanomaterials have been widely studied, and applied in diverse industries 1-3. A number of carbon nanostructures have been synthesized and applied in different fields. The 0D carbon nanomaterials include clusters, quantum dots, nanoflakes, and buckyballs 3. Among them, the C 60 fullerene molecule (containing 12 pentagons and 20 hexagons), where the carbon atoms are sp 2-sp 3-hybridized, has been a popular carbon nanomaterial 1. The discovery of C 60 has led to the flourishment of carbon nanomaterials in various ways. Graphite is a bulk layered material, where the sp 2-hybridized carbon atoms in each layer are arranged in a hexagonal lattice. The 2D carbon nanomaterial, graphene, can be obtained by mechanically exfoliating a single layer of carbon atoms from graphite 2. Thus, graphene, which is a perfect arrangement of hexagons made up of sp 2-hybridized carbon atoms in a 2D planar surface, can be the thinnest (i.e., single-atom-thick) material synthesized ever. Graphene is a zero-gap semiconductor or semimetal with massless Dirac fermions with linear dispersion at low energy. Because of the Dirac-cone feature, graphene has huge potential in electronics applications 2. The discovery of graphene has also led to the discovery of other 2D materials. Besides, if a graphene sheet can be rolled up to form a seamless cylinder, one obtains a carbon nanotube (CNT), which belongs to the class of 1D nanostructures. Note that CNTs were first observed by Iijima in 19...

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From Cyclic Nanorings to Single-Walled Carbon Nanotubes: Disclosing the Evolution of their Electronic Structure with the Help of Theoretical Methods

Cited by 6 publications

References 27 publications

Investigating the (Poly)Radicaloid Nature of Real-World Organic Compounds with DFT-Based Methods

Investigating the (Poly)Radicaloid Nature of Real-World Organic Compounds with DFT-Based Methods

Frustrated magnetic interactions in a cyclacene crystal

TAO-DFT investigation of electronic properties of linear and cyclic carbon chains

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