Abstract
Reliable prediction of the properties of nanosystems with radical nature has been tremendously challenging for common computational approaches. Aiming to overcome this, we employ thermally-assisted-occupation density functional theory (TAO-DFT) to investigate various electronic properties (e.g., singlet–triplet energy gaps, vertical ionization potentials, vertical electron affinities, fundamental gaps, symmetrized von Neumann entropy, active orbital occupation numbers, and visualization of active orbitals) associated with a series of triangle-shaped graphene nanoflakes with n fused benzene rings at each side (denoted as n-triangulenes), which can be extended from triangulene. According to our TAO-DFT results, the ground states of n-triangulenes are singlets for all the values of n studied (n = 3, 5, 7, 9, ..., and 21). Moreover, the larger the values of n, the more significant the polyradical nature of n-triangulenes. There are approximately (n – 1) unpaired electrons for the ground state of n-triangulene. The increasing polyradical nature of the larger n-triangulenes should be closely related to the fact that the active orbitals tend to be mainly concentrated at the periphery of n-triangulenes, apparently increasing with the molecular size.
Highlights
Because of its promising properties and potential applications, graphene has been extensively studied by several researchers in recent years.[1−6] For instance, the high carrier mobility, saturation velocity, and long spin diffusion length of graphene have yielded the possibility of developing fascinating electronics and spintronics based on graphene.[1,2,6] owing to the lack of an energy band gap, graphene is not suitable for transistor applications
With the aim to study the ground-state properties of nanosystems with radical nature at low computational cost with reasonable accuracy, we have recently developed thermally-assisted-occupation density functional theory (TAO-DFT),[15] a density functional theory with fractional orbital occupations produced by the Fermi−Dirac distribution function
We have investigated the electronic properties, such as EST, IPv, EAv, Eg, SvN, active orbital occupation numbers, and visualization of active orbitals, of n-triangulenes (n = 3, 5, 7, 9, ..., and 21) using TAO-DFT due to its decent balance between cost and performance for studying nanosystems with radical nature
Summary
Because of its promising properties and potential applications, graphene has been extensively studied by several researchers in recent years.[1−6] For instance, the high carrier mobility, saturation velocity, and long spin diffusion length of graphene have yielded the possibility of developing fascinating electronics and spintronics based on graphene.[1,2,6] owing to the lack of an energy band gap, graphene is not suitable for transistor applications. Owing to an excellent trade-off between computational cost and accuracy, employing TAO-DFT for a comprehensive study on graphene nanoflakes with different shapes, edges, and sizes is well-justified. It is computationally intractable to carry out sufficiently accurate multireference electronic structure calculations for n-triangulenes, especially for those with the larger n values It remains tremendously challenging for common computation approaches to reliably describe the ground-state properties of the larger ntriangulenes. With the aim to study the ground-state properties of nanosystems with radical nature at low computational cost with reasonable accuracy, we have recently developed thermally-assisted-occupation density functional theory (TAO-DFT),[15] a density functional theory with fractional orbital occupations produced by the Fermi−Dirac distribution function. As TAO-DFT is computationally efficient (i.e., similar to KS-DFT), we have employed TAO-DFT for the study of the electronic properties of various nanosystems with radical nature in recent years.[20,22,44−49] Very recently, TAO-DFT and related approaches have been employed for the study of the
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
