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Seenithurai S, Chai JD. Electronic Properties of Graphene Nano-Parallelograms: A Thermally Assisted Occupation DFT Computational Study. Molecules 2024; 29:349. [PMID: 38257262 PMCID: PMC11154290 DOI: 10.3390/molecules29020349] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Revised: 01/05/2024] [Accepted: 01/08/2024] [Indexed: 01/24/2024] Open
Abstract
In this computational study, we investigate the electronic properties of zigzag graphene nano-parallelograms (GNPs), which are parallelogram-shaped graphene nanoribbons of various widths and lengths, using thermally assisted occupation density functional theory (TAO-DFT). Our calculations revealed a monotonic decrease in the singlet-triplet energy gap as the GNP length increased. The GNPs possessed singlet ground states for all the cases examined. With the increase of GNP length, the vertical ionization potential and fundamental gap decreased monotonically, while the vertical electron affinity increased monotonically. Some of the GNPs studied were found to possess fundamental gaps in the range of 1-3 eV, lying in the ideal region relevant to solar energy applications. Besides, as the GNP length increased, the symmetrized von Neumann entropy increased monotonically, denoting an increase in the degree of the multi-reference character associated with the ground state GNPs. The occupation numbers and real-space representation of active orbitals indicated that there was a transition from the nonradical nature of the shorter GNPs to the increasing polyradical nature of the longer GNPs. In addition, the edge/corner localization of the active orbitals was found for the wider and longer GNPs.
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Affiliation(s)
- Sonai Seenithurai
- Department of Physics, National Taiwan University, Taipei 10617, Taiwan;
| | - Jeng-Da Chai
- Department of Physics, National Taiwan University, Taipei 10617, Taiwan;
- Center for Theoretical Physics and Center for Quantum Science and Engineering, National Taiwan University, Taipei 10617, Taiwan
- Physics Division, National Center for Theoretical Sciences, Taipei 10617, Taiwan
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Tsai HY, Chai JD. Real-Time Extension of TAO-DFT. Molecules 2023; 28:7247. [PMID: 37959667 PMCID: PMC10647330 DOI: 10.3390/molecules28217247] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2023] [Revised: 10/19/2023] [Accepted: 10/21/2023] [Indexed: 11/15/2023] Open
Abstract
Thermally assisted occupation density functional theory (TAO-DFT) has been an efficient electronic structure method for studying the ground-state properties of large electronic systems with multi-reference character over the past few years. To explore the time-dependent (TD) properties of electronic systems (e.g., subject to an intense laser pulse), in this work, we propose a real-time (RT) extension of TAO-DFT, denoted as RT-TAO-DFT. Moreover, we employ RT-TAO-DFT to study the high-order harmonic generation (HHG) spectra and related TD properties of molecular hydrogen H2 at the equilibrium and stretched geometries, aligned along the polarization of an intense linearly polarized laser pulse. The TD properties obtained with RT-TAO-DFT are compared with those obtained with the widely used time-dependent Kohn-Sham (TDKS) method. In addition, issues related to the possible spin-symmetry breaking effects in the TD properties are discussed.
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Affiliation(s)
- Hung-Yi Tsai
- Department of Physics, National Taiwan University, Taipei 10617, Taiwan;
| | - Jeng-Da Chai
- Department of Physics, National Taiwan University, Taipei 10617, Taiwan;
- Center for Theoretical Physics and Center for Quantum Science and Engineering, National Taiwan University, Taipei 10617, Taiwan
- Physics Division, National Center for Theoretical Sciences, Taipei 10617, Taiwan
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Seenithurai S, Chai JD. TAO-DFT with the Polarizable Continuum Model. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 13:nano13101593. [PMID: 37242010 DOI: 10.3390/nano13101593] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Revised: 05/07/2023] [Accepted: 05/08/2023] [Indexed: 05/28/2023]
Abstract
For the ground-state properties of gas-phase nanomolecules with multi-reference character, thermally assisted occupation (TAO) density functional theory (DFT) has recently been found to outperform the widely used Kohn-Sham DFT when traditional exchange-correlation energy functionals are employed. Aiming to explore solvation effects on the ground-state properties of nanomolecules with multi-reference character at a minimal computational cost, we combined TAO-DFT with the PCM (polarizable continuum model). In order to show its usefulness, TAO-DFT-based PCM (TAO-PCM) was used to predict the electronic properties of linear acenes in three different solvents (toluene, chlorobenzene, and water). According to TAO-PCM, in the presence of these solvents, the smaller acenes should have nonradical character, and the larger ones should have increasing polyradical character, revealing striking similarities to the past findings in the gas phase.
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Affiliation(s)
- Sonai Seenithurai
- Department of Physics, National Taiwan University, Taipei 10617, Taiwan
| | - Jeng-Da Chai
- Department of Physics, National Taiwan University, Taipei 10617, Taiwan
- Center for Theoretical Physics and Center for Quantum Science and Engineering, National Taiwan University, Taipei 10617, Taiwan
- Physics Division, National Center for Theoretical Sciences, Taipei 10617, Taiwan
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Morales-Guevara R, Fuentes JA, Páez-Hernández D, Carreño A. Intramolecular Hydrogen Bond in Pyridine Schiff Bases as Ancillary Ligands of Re(I) Complexes Is a Switcher between Visible and NIR Emissions: A Relativistic Quantum Chemistry Study. J Phys Chem A 2022; 126:8997-9007. [PMID: 36413983 DOI: 10.1021/acs.jpca.2c06435] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Rhenium(I) tricarbonyl complexes have been described as suitable fluorophores, particularly for biological applications. fac-[Re(CO)3(N,N)L](0 or 1+) complexes, where N,N is a substituted dinitrogenated ligand (bipyridine or derivatives with relatively small substituents) and L the ancillary ligand [a pyridine Schiff base (PSB) harboring an intramolecular hydrogen bond (IHB)], have presented promissory results concerning their use as fluorophores, especially for walled cells (i.e., bacteria and fungi). In this work, we present a relativistic theoretical analysis of two series of fac-[Re(CO)3(N,N)PSB]1+ complexes to predict the role of the IHB in the ancillary ligand concerning their photophysical behavior. N,N corresponds to 2,2'-bipyridine (bpy) (series A) or 4,4'-bis(ethoxycarbonyl)-2,2'-bipyridine (deeb) (series B). We found that all the complexes present absorption in the visible light range. In addition, complexes presenting a PSB with an IHB exhibit luminescent emission suitable for biological purposes: large Stokes shift, emission in the range of 600-700 nm, and τ in the order of 10-2 to 10-3 s. By contrast, complexes with PSB lacking the IHB show a predicted emission with the lowest triplet excited-state energy entering the NIR region. These results suggest a role of the IHB as an important switcher between visible and NIR emissions in this kind of complexes. Since the PSB can be substituted to modulate the properties of the whole Re(I) complex, it will be interesting to explore whether other substitutions can also affect the photophysical properties, mainly the emission range.
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Affiliation(s)
- Rosaly Morales-Guevara
- Programa de Doctorado en Físicoquímica Molecular, Facultad de Ciencias Exactas, Universidad Andres Bello, Santiago 8370146, Chile.,Laboratory of Organometallic Synthesis, Center of Applied NanoSciences (CANS), Facultad de Ciencias Exactas, Universidad Andrés Bello, República 330, Santiago 8370186, Chile
| | - Juan A Fuentes
- Laboratorio de Genética y Patogénesis Bacteriana, Facultad de Ciencias de la Vida, Universidad Andrés Bello, República 330, Santiago 8370186, Chile
| | - Dayán Páez-Hernández
- Programa de Doctorado en Físicoquímica Molecular, Facultad de Ciencias Exactas, Universidad Andres Bello, Santiago 8370146, Chile.,Laboratory of Organometallic Synthesis, Center of Applied NanoSciences (CANS), Facultad de Ciencias Exactas, Universidad Andrés Bello, República 330, Santiago 8370186, Chile
| | - Alexander Carreño
- Programa de Doctorado en Físicoquímica Molecular, Facultad de Ciencias Exactas, Universidad Andres Bello, Santiago 8370146, Chile.,Laboratory of Organometallic Synthesis, Center of Applied NanoSciences (CANS), Facultad de Ciencias Exactas, Universidad Andrés Bello, República 330, Santiago 8370186, Chile
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Chen CC, Chai JD. Electronic Properties of Hexagonal Graphene Quantum Rings from TAO-DFT. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:nano12223943. [PMID: 36432229 PMCID: PMC9694783 DOI: 10.3390/nano12223943] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Revised: 11/04/2022] [Accepted: 11/06/2022] [Indexed: 06/01/2023]
Abstract
The reliable prediction of electronic properties associated with graphene nanosystems can be challenging for conventional electronic structure methods, such as Kohn-Sham (KS) density functional theory (DFT), due to the presence of strong static correlation effects in these systems. To address this challenge, TAO (thermally assisted occupation) DFT has been recently proposed. In the present study, we employ TAO-DFT to predict the electronic properties of n-HGQRs (i.e., the hexagonal graphene quantum rings consisting of n aromatic rings fused together at each side). From TAO-DFT, the ground states of n-HGQRs are singlets for all the cases investigated (n = 3-15). As the system size increases, there should be a transition from the nonradical to polyradical nature of ground-state n-HGQR. The latter should be intimately related to the localization of active TAO-orbitals at the inner and outer edges of n-HGQR, which increases with increasing system size.
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Affiliation(s)
- Chi-Chun Chen
- Department of Physics, National Taiwan University, Taipei 10617, Taiwan
| | - Jeng-Da Chai
- Department of Physics, National Taiwan University, Taipei 10617, Taiwan
- Center for Theoretical Physics and Center for Quantum Science and Engineering, National Taiwan University, Taipei 10617, Taiwan
- Physics Division, National Center for Theoretical Sciences, Taipei 10617, Taiwan
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