Electronic Properties of Linear and Cyclic Boron Nanoribbons from Thermally-Assisted-Occupation Density Functional Theory

Seenithurai, S.; Chai, Jeng-Da

doi:10.1038/s41598-019-48560-z

Cited by 14 publications

(22 citation statements)

References 66 publications

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“…(3) , we calculate the symmetrized von Neumann entropy 16,50,51,54,[56][57][58][59][60][61][62]69 using spin-unrestricted TAO-LDA. Here, the occupation number f i,σ of the i th σ-spin orbital (i.e., up-spin orbital or down-spin orbital) obtained with spin-unrestricted TAO-LDA, which ranges from 0 to 1, is closely related to the occupation number of the i th σ-spin natural orbital 49-51 .…”

Section: Vertical Ionization Potential Vertical Electron Affinity Amentioning

confidence: 99%

“…Besides, aiming to improve the accuracy of TAO-DFT for a wide range of applications, a self-consistent scheme determining the fictitious temperature θ in TAO-DFT has been recently proposed 53 . Since TAO-DFT is a computationally efficient electronic structure method, a number of strongly correlated electron systems at the nanoscale have been studied using TAO-DFT in recent years 16,[54][55][56][57][58][59][60][61][62] . Besides, TAO-DFT has been recently shown to be useful in describing the vibrational spectra of molecules with radical nature 63 .…”

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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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Section: Vertical Ionization Potential Vertical Electron Affinity Amentioning

confidence: 99%

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confidence: 99%

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

Seenithurai

Chai

2020

Sci Rep

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“…For n-acene (containing N e electrons), we define the HOMO (i.e., highest occupied molecular orbital) as the (N e /2)th orbital, the LUMO (i.e., lowest unoccupied molecular orbital) as the (N e /2 + 1)th orbital, and so forth (Chai, 2012(Chai, , 2017Wu and Chai, 2015;Wu et al, 2016;Yeh et al, 2018;Chung and Chai, 2019;Deng and Chai, 2019;Seenithurai and Chai, 2019;Huang et al, 2020). For brevity, HOMO and LUMO are denoted as H and L, respectively.…”

Section: Active Orbital Occupation Numbersmentioning

confidence: 99%

TAO-DFT-Based Ab Initio Molecular Dynamics

Chai

2020

Front. Chem.

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Recently, AIMD (ab initio molecular dynamics) has been extensively employed to explore the dynamical information of electronic systems. However, it remains extremely challenging to reliably predict the properties of nanosystems with a radical nature using conventional electronic structure methods (e.g., Kohn-Sham density functional theory) due to the presence of static correlation. To address this challenge, we combine the recently formulated TAO-DFT (thermally-assisted-occupation density functional theory) with AIMD. The resulting TAO-AIMD method is employed to investigate the instantaneous/average radical nature and infrared spectra of n-acenes containing n linearly fused benzene rings (n = 2-8) at 300 K. According to the TAO-AIMD simulations, on average, the smaller n-acenes (up to n = 5) possess a nonradical nature, and the larger n-acenes (n = 6-8) possess an increasing radical nature, showing remarkable similarities to the ground-state counterparts at 0 K. Besides, the infrared spectra of n-acenes obtained with the TAO-AIMD simulations are in qualitative agreement with the existing experimental data.

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“…Besides, to improve the overall accuracy of TAO-DFT for diverse applications, an approach that determines the self-consistent value of

in TAO-DFT has been recently formulated [ 44 ]. Also, to comment on its applicability, TAO-DFT has been widely adopted for electronic structure calculations [ 5 , 12 , 15 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 ], hydrogen storage applications [ 46 , 48 , 49 ], and vibrational analysis [ 54 ], especially for nanosystems possessing radical character. Furthermore, in several recent investigations [ 5 , 37 , 39 , 40 , 42 , 45 ], the occupation numbers of orbitals from TAO-DFT have been shown to be close to the occupation numbers of natural orbitals obtained with the variational two-electron reduced-density-matrix-driven CASSCF (v2RDM-CASSCF) method, which is an accurate MR electronic structure method, leading to a qualitatively similar tendency in describing the radical nature associated with various PAHs.…”

Section: Introductionmentioning

confidence: 99%

TAO-DFT Study on the Electronic Properties of Diamond-Shaped Graphene Nanoflakes

2020

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At the nanoscale, it has been rather troublesome to properly explore the properties associated with electronic systems exhibiting a radical nature using traditional electronic structure methods. Graphene nanoflakes, which are graphene nanostructures of different shapes and sizes, are typical examples. Recently, TAO-DFT (i.e., thermally-assisted-occupation density functional theory) has been formulated to tackle such challenging problems. As a result, we adopt TAO-DFT to explore the electronic properties associated with diamond-shaped graphene nanoflakes with n = 2–15 benzenoid rings fused together at each side, designated as n-pyrenes (as they could be expanded from pyrene). For all the n values considered, n-pyrenes are ground-state singlets. With increasing the size of n-pyrene, the singlet-triplet energy gap, vertical ionization potential, and fundamental gap monotonically decrease, while the vertical electron affinity and symmetrized von Neumann entropy (which is a quantitative measure of radical nature) monotonically increase. When n increases, there is a smooth transition from the nonradical character of the smaller n-pyrenes to the increasing polyradical nature of the larger n-pyrenes. Furthermore, the latter is shown to be related to the increasing concentration of active orbitals on the zigzag edges of the larger n-pyrenes.

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Electronic Properties of Linear and Cyclic Boron Nanoribbons from Thermally-Assisted-Occupation Density Functional Theory

Cited by 14 publications

References 66 publications

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

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

TAO-DFT-Based Ab Initio Molecular Dynamics

TAO-DFT Study on the Electronic Properties of Diamond-Shaped Graphene Nanoflakes

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