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density functional theory

M E Sánchez Vergara, R Salcedo, Bertha Molina, R Carrera-Téllez, J R Álvarez-Bada, A Hernández-García, V Gómez-Vidales
The present study reports the doping of a semiconducting molecular material through the formation of hydrogen bonds between the macrocycle Cu(II)(TAAB) and the electronic acceptor TCNQ. According to density functional theory (DFT) calculations and electron paramagnetic resonance (EPR) analysis, the doped compound has the shape of a distorted square pyramid, with four nitrogen atoms in the equatorial position and the apical oxygen atom from the water ligands. These water molecules can generate strong hydrogen bonds with TCNQ and the TAAB metallic complex...
April 11, 2018: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Brendan J Gifford, Andrew E Sifain, Han Htoon, Stephen K Doorn, Svetlana V Kilina, Sergei Tretiak
Covalent functionalization of single-walled carbon nanotubes (SWCNTs) introduces redshifted emission features in the near-infrared spectral range due to exciton localization around the defect site. Such chemical modifications increase SWCNT potential for use as near-infrared emitters and single-photon sources in telecommunications applications. Density Functional Theory (DFT)-based studies on finite-length models of SWCNTs have quantified reorganization energies and optical transitions dependent on chemical functionalization...
April 20, 2018: Journal of Physical Chemistry Letters
Seung Mi Lee, Min-Young Kim, Young Heon Kim
We investigated the effects of strain on the electronic structures of InAsxP1-x using quantum mechanical density functional theory calculations. The electronic band gap and electron effective mass decreased with the increase of the uniaxial tensile strain along the [0001] direction of wurtzite InAs0.75P0.25. Therefore, faster electron movements are expected. These theoretical results are in good agreement with the experimental measurements of InAs0.75P0.25 nanowire.
September 1, 2018: Journal of Nanoscience and Nanotechnology
Geon Hyeong Lee, Young Sik Kim
A novel quinoxaline-based organic dye with heteroleptic dual electron donors (phenoxazine and carbazole) on each side of a quinoxaline was designed, and its electronic and optical properties were investigated theoretically for applications to dye-sensitized solar cells (DSSCs). To understand the factors influencing the photovoltaic efficiency, density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations of these dyes were performed. The absorption spectrum of the dyes showed different forms because of the different energy levels of the molecular orbital (MO) of each dye and the intramolecular charge-transfer (ICT) characteristics...
September 1, 2018: Journal of Nanoscience and Nanotechnology
Geon Hyeong Lee, Young Sik Kim
In this study, phenoxazine (PXZ)-based dye sensitizers with triphenylamine (TPA) as a dual-electron donor and thiophen and benzothiadiazole (BTD) or 4,7-diethynylbenzo[c][1,2,5]thiadiazole (DEBT) as an electron acceptor (dye1, dye2, and dye3) were designed and investigated. dye3 can significantly stabilize the lowest unoccupied molecular orbital (LUMO) energy level of an organic dye. We used density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations to better understand the factors responsible for the photovoltaic performance...
September 1, 2018: Journal of Nanoscience and Nanotechnology
Geon Hyeong Lee, Young Sik Kim
Novel thermally activated delayed fluorescence (TADF) materials with benzofuro[2,3-b]pyridine (BFPd) as an electron acceptor and carbazole derivatives [carbazole (Cz), 1,3,6,8-tetramethyl-9H-carbazole (tmCz), and 9'H-9,3':6',9''-tercarbazole (terCz)] as electron donors are designed, and their electronic and optical properties are investigated theoretically for a deep blue organic light-emitting diode (OLED). We obtain the energies of the first singlet (S1) and first triplet (T1) excited states of TADF materials by performing density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations on the ground state by using the dependence on charge transfer amounts for the optimal Hartree-Fock percentage in the exchange-correlation of TD-DFT...
September 1, 2018: Journal of Nanoscience and Nanotechnology
Geon Hyeong Lee, Young Sik Kim
Novel thermally activated delayed fluorescence (TADF) materials including 10H-phenoxaborin (PXB) as an electron acceptor and carbazole derivatives [carbazole (Cz), 1-methyl-carbazole (1-m-Cz), and 3,6-bis(3,6-diphenylcarbazolyl)carbazole (BDPCC)] as electron donors (Cz-PXB, 1-m-Cz-PXB, and BDPCC-PXB) were designed and investigated theoretically for deep blue organic light-emitting diode (OLED). Using density functional theory (DFT) and time-dependent DFT calculations, we obtained the electron distribution of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) and the energy of the lowest singlet (S1) and the lowest triplet (T1) excited states...
September 1, 2018: Journal of Nanoscience and Nanotechnology
Jianling Li, Guohua Ding, Yanyan Niu, Luyong Wu, Huajie Feng, Wenying He
5-Methyl-2-phenyl-2H-1,2,3-triazole-4-carboxylic acid (MPTC), a newly synthesized compound, was explored to study the structural properties and theoretical spectra by using GaussView5.0 program package and the time dependent density functional theory (TD DFT). The calculated quantum chemical values suggested that it is easy for MPTC to lose electron with weak electron accepting ability. And the results of experimental measurements on fluorescence and absorption spectra were consistent with that of the calculated spectra in great degree...
April 11, 2018: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
María Blanco-Rey, Ane Sarasola, Corneliu Nistor, Luca Persichetti, Christian Stamm, Cinthia Piamonteze, Pietro Gambardella, Sebastian Stepanow, Mikhail M Otrokov, Vitaly N Golovach, Andres Arnau
The magnetic anisotropy and exchange coupling between spins localized at the positions of 3d transition metal atoms forming two-dimensional metal⁻organic coordination networks (MOCNs) grown on a Au(111) metal surface are studied. In particular, we consider MOCNs made of Ni or Mn metal centers linked by 7,7,8,8-tetracyanoquinodimethane (TCNQ) organic ligands, which form rectangular networks with 1:1 stoichiometry. Based on the analysis of X-ray magnetic circular dichroism (XMCD) data taken at T = 2.5 K, we find that Ni atoms in the Ni⁻TCNQ MOCNs are coupled ferromagnetically and do not show any significant magnetic anisotropy, while Mn atoms in the Mn⁻TCNQ MOCNs are coupled antiferromagnetically and do show a weak magnetic anisotropy with in-plane magnetization...
April 20, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Elena Meirzadeh, Isabelle Weissbuch, David Ehre, Meir Lahav, Igor Lubomirsky
Crystals are physical arrays delineated by polar surfaces and often contain imperfections of a polar nature. Understanding the structure of such defects on the molecular level is of topical importance since they strongly affect the macroscopic properties of materials. Moreover, polar imperfections in crystals can be created intentionally and specifically designed by doping nonpolar crystals with "tailor-made" additives as dopants, since their incorporation generally takes place in a polar mode. Insertion of dopants also induces a polar deformation of neighboring host molecules, resulting in the creation of polar domains within the crystals...
April 20, 2018: Accounts of Chemical Research
Jon Uranga, Jon I Mujika, Rafael Grande-Aztatzi, Jon M Matxain
Hydroxyl radical (●OH) is known to be highly reactive. Herein, we analyze the oxidation of acid (Asp and Glu), base (Arg and Lys) and amide (Asn and Gln) containing amino acids by the consecutive attack of two ●OH. In this work we study the reaction pathway by means of density functional theory. The oxidation mechanism is divided into two steps: 1) the first ●OH can abstract a H atom or an electron, leading to a radical amino acid derivative, which is the intermediate of the reaction 2) the second ●OH can abstract another H atom or add itself to the formed radical, rendering the final oxidized products...
April 20, 2018: Journal of Physical Chemistry. B
S Liu, D Baugh, K Motobayashi, X Zhao, S V Levchenko, S Gawinkowski, J Waluk, L Grill, M Persson, T Kumagai
Anharmonicity plays a crucial role in hydrogen transfer reactions in hydrogen-bonding systems, which leads to a peculiar spectral line shape of the hydrogen stretching mode as well as highly complex intra/intermolecular vibrational energy relaxation. Single-molecule study with a well-defined model is necessary to elucidate a fundamental mechanism. Recent low-temperature scanning tunnelling microscopy (STM) experiments revealed that the cis ↔ cis tautomerization in a single porphycene molecule on Cu(110) at 5 K can be induced by vibrational excitation via an inelastic electron tunnelling process and the N-H(D) stretching mode couples with the tautomerization coordinate [Kumagai et al...
April 20, 2018: Physical Chemistry Chemical Physics: PCCP
Cloé Azarias, Miguel Ponce-Vargas, Isabelle Navizet, Paul Fleurat-Lessard, Anthony Romieu, Boris Le Guennic, Jean-Alexandre Richard, Denis Jacquemin
Using a computational approach combining the Time-Dependent Density Functional Theory (TD-DFT) and the second-order Coupled Cluster (CC2) approaches, we investigate the spectral properties of a large panel of nor-dihydroxanthene (DHX)-hemicyanine fused dyes. First we compare the theoretical and experimental 0-0 energies for a set of 14 known synthetic compounds and show that a remarkable agreement between theory and experiment is obtained when a suitable environmental model is selected. In addition, we obtain vibrationally-resolved spectra for several compounds and theory also accurately reproduces the experimental band shapes...
April 20, 2018: Physical Chemistry Chemical Physics: PCCP
Jiabo Le, Qiyuan Fan, Laura Perez-Martinez, Angel Cuesta, Jun Cheng
Understanding the structures of electrochemical interfaces at the atomic level is key to developing efficient electrochemical cells for energy storage and conversion. Spectroscopic techniques have been widely used to investigate the structures and vibrational properties of the interfaces. The interpretation of these spectra is however not straightforward. In this work, density functional theory based molecular dynamics simulations were performed to study the vibrational properties of the Pt(111)- and Au(111)-water interfaces...
April 20, 2018: Physical Chemistry Chemical Physics: PCCP
Keisuke Wada, Ken Sakaushi, Sono Sasaki, Hiroshi Nishihara
Metallically-conductive bis(diimino)nickel framework (NiDI), an emerging class of metal-organic framework (MOF) analogues consisting of two-dimensional (2D) coordination networks, was found to show an energy storage principle using both cation- and anion-insertion. This principle gives high energy led by a multielectron transfer reaction: its specific capacity is one of the highest among MOF-based cathode materials in rechargeable energy storage devices, with stable cycling performance up to 300 cycles. This mechanism was studied by a wide spectrum of electrochemical techniques combined with density-functional theory calculations...
April 19, 2018: Angewandte Chemie
Xue-Rui Wang, Jie-Yu Liu, Zi-Wei Liu, Wei-Chao Wang, Jun Luo, Xiao-Peng Han, Xi-Wen Du, Shi-Zhang Qiao, Jing Yang
For many regenerative electrochemical energy-conversion systems, hybrid electrocatalysts comprising transition metal (TM) oxides and heteroatom-doped (e.g., nitrogen-doped) carbonaceous materials are promising bifunctional oxygen reduction reaction/oxygen evolution reaction electrocatalysts, whose enhanced electrocatalytic activities are attributed to the synergistic effect originated from the TM-N-C active sites. However, it is still ambiguous which configuration of nitrogen dopants, either pyridinic or pyrrolic N, when bonded to the TM in oxides, predominately contributes to the synergistic effect...
April 20, 2018: Advanced Materials
Yesim Mogulkoc, Mohsen Modarresi, Aybey Mogulkoc, Bora Alkan
The van der Waals (vdW) heterostructures are emerging as promising structures for future possible optoelectronic devices. Motivated by the recent studies on vdW heterostructures with their fascinating physical properties, we investigate the electronic and optical properties of boron phosphide/blue phosphorus heterostructures in the framework of density functional theory (DFT) and tight-binding (TB) approximations. We analyze the variation of the energy band gap, the characteristics of the energy band diagram, charge redistribution by stacking and the electrostatic potential along the perpendicular direction...
April 20, 2018: Physical Chemistry Chemical Physics: PCCP
José I Martínez, Alex Laikhtman, Hoi Ri Moon, Alla Zak, Julio A Alonso
Understanding the interaction of hydrogen with layered materials is crucial in the fields of sensors, catalysis, fuel cells and hydrogen storage, among others. Density functional theory, improved by the introduction of van der Waals dispersion forces, provides an efficient and practical workbench to investigate the interaction of molecular and atomic hydrogen with WS2 multilayers and nanotubes. We find that H2 physisorbs on the surface of those materials on top of W atoms, while atomic H chemisorbs on top of S atoms...
April 20, 2018: Physical Chemistry Chemical Physics: PCCP
E T Sato, H Martinho
Vibrational spectroscopy has been widely employed to unravel the physical-chemical properties of biological systems. Due to its high sensitivity to monitoring real time " in situ " changes, Raman spectroscopy has been successfully employed, e.g., in biomedicine, metabolomics, and biomedical engineering. The interpretation of Raman spectra in these cases is based on the isolated macromolecules constituent vibrational assignment. Due to this, probing the anharmonic or the mutual interactions among specific moieties/side chains is a challenge...
April 1, 2018: Biomedical Optics Express
Jinfeng Liu, Xiao He, John Z H Zhang, Lian-Wen Qi
An accurate and efficient ab initio molecular dynamics (AIMD) simulation of liquid water was made possible using the fragment-based approach (J. F. Liu, X. He and J. Z. H. Zhang, Phys. Chem. Chem. Phys. , 2017, 19 , 11931-11936). In this study, we advance the AIMD simulations using the fragment-based coupled cluster (CC) theory, more accurately revealing the structural and dynamical properties of liquid water under ambient conditions. The results show that the double-donor hydrogen-bond configurations in liquid water are nearly in balance with the single-donor configurations, with a slight bias towards the former...
February 28, 2018: Chemical Science
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