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density functional theory

Debarati Dey, Pradipta Roy, Debashis De
The Field Effect Transistor (FET) characteristics has been observed from a single-walled Adenine nanotube device using Density Functional Theory associated with Non Equilibrium Green's Function based First Principle approach. This device is electrically doped which shows both n and p channel characteristics of a p-i-n FET. This device is designed and originated from a single-walled biomolecular nanotube structure. The p and n regions have been induced at the two ends of the device using electrical doping process...
July 10, 2017: Journal of Molecular Graphics & Modelling
Adam Philips, Alex Marchenko, Lionel Alexandre Truflandier, Jochen Autschbach
Quadrupolar NMR relaxation rates are computed for (17)O, (2)H nuclei of liquid water, and of (23)Na(+) , and (35)Cl(-) in aqueous solution, via Kohn-Sham (KS) density functional theory ab-initio molecular dynamics (aiMD) and subsequent KS electric field gradient (EFG) calculations along the trajectories. The calculated relaxation rates are within about a factor of two of experimental results, and improved over previous aiMD simulations. The relaxation rates are assessed with regard to the lengths of the simulations as well as configurational sampling...
July 18, 2017: Journal of Chemical Theory and Computation
Jing-Shuang Dang, Wei-Wei Wang, Jia-Jia Zheng, Shigeru Nagase, Xiang Zhao
Although the existence of Stone-Wales (5-7) defect at graphene edge has been clarified experimentally, theoretical study on the formation mechanism is still imperfect. In particular, the regioselectivity of multistep reactions at edge (self-reconstruction and growth with foreign carbon feedstock) is essential to understand the kinetic behavior of reactive boundaries but investigations are still lacking. Herein, by using finite-sized models, multistep reconstructions and carbon dimer additions of a bared zigzag edge are introduced using density functional theory calculations...
July 18, 2017: Journal of Computational Chemistry
Ryosuke Ishizuka, Nobuyuki Matubayasi
A self-consistent scheme combining the molecular dynamics (MD) simulation and density functional theory (DFT) was recently proposed to incorporate the effects of the charge transfer and polarization of ions into non-poralizable force fields of ionic liquids for improved description of energetics and dynamics. The purpose of the present work is to analyze the detailed setups of the MD/DFT scheme by focusing on how the basis set, exchange-correlation (XC) functional, charge-fitting method or force field for the intramolecular and Lennard-Jones interactions affects the MD/DFT results of 1,3-dimethylimidazolium bis(trifluoromethylsulfonyl) imide ( [C1mim][NTf2]) and 1-ethyl-3-methylimidazolium glycinate ( [C2mim][Gly])...
July 18, 2017: Journal of Computational Chemistry
Haiyan Yuan, Pin Xiao, Yiying Zheng, Jingping Zhang
Silver-mediated hydroazidation of unactivated alkynes has been developed as a new method for the synthesis of vinyl azides. Density functional theory calculations toward this reaction reveal that terminal alkynes with TMS-N3 participated hydroazidation proceed through HN3 formation, deprotonation and silver acetylides formation, nucleophilic addition, and protonation of terminal carbon by AgHCO3 . It is also found that water molecules and activation modes of Ag (I) have a significant influence on the title reaction mechanism...
July 18, 2017: Journal of Computational Chemistry
Bun Chan, Yukio Kawashima, Kimihiko Hirao
In the present study, we have explored several prospects for the further development of screened-exchange density functional theory (SX-DFT) procedures. Using the performance of HSE06 as our measure, we find that the use of alternative correlation functionals (as oppose to PBEc in HSE06) also yields adequate results for a diverse set of thermochemical properties. We have further examined the performance of new SX-DFT procedures (termed HSEB-type methods) that comprise the HSEx exchange and a (near-optimal) reparametrized B97c (cOS,0  = cSS,0  = 1, cOS,1  = -1...
July 18, 2017: Journal of Computational Chemistry
Natalia Berseneva, Hannu-Pekka Komsa, Ville Vierimaa, Torbjörn Björkman, Zheyong Fan, Ari Harju, Milica Todorović, Arkady Krasheninnikov, Risto M Nieminen
Development of spatially homogeneous mixed structures with boron (B), nitrogen (N) and carbon (C) atoms arranged in a honeycomb lattice is highly desirable, as they open a possibility to create stable two-dimensional materials with tunable band gaps. However, at least in the free-standing form, the mixed BCN system is energetically driven towards phase segregation to graphene and hexagonal BN. It is possible to overcome the segregation when BCN material is grown on a particular metal substrate, for example Ru(0001), but the stabilization mechanism is still unknown...
July 18, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Chen Guo, Shuxian Wei, Sainan Zhou, Tian Zhang, Zhaojie Wang, Siu Pang Ng, Xiaoqing Lu, Chi-Man Lawrence Wu, Wenyue Guo
Surface modification by metal doping is an effective treatment technique for improving surface properties for CO2 reduction. Herein, the effects of doped Pd, Ru, and Cu on the adsorption, activation, and reduction selectivity of CO2 on CeO2(111) were investigated by periodic density functional theory. The doped metals distorted the configuration of a perfect CeO2(111) by weakening the adjacent Ce-O bond strength, and Pd doping was beneficial for generating a highly active O vacancy. The analyses of adsorption energy, charge density difference, and density of states confirmed that the doped metals were conducive for enhancing CO2 adsorption, especially for Cu/CeO2(111)...
July 18, 2017: ACS Applied Materials & Interfaces
Caroline R Kwawu, Richard Tia, Evans Adei, Nelson Y Dzade, C Richard A Catlow, Nora H de Leeuw
We have used spin polarized density functional theory calculations to perform extensive mechanistic studies of CO2 dissociation into CO and O on the clean Fe(100), (110) and (111) surfaces and on the same surfaces coated by a monolayer of nickel. CO2 chemisorbs on all three bare facets and binds more strongly to the stepped (111) surface than on the open flat (100) and close-packed (110) surfaces, with adsorption energies of -88.7 kJ mol(-1), -70.8 kJ mol(-1) and -116.8 kJ mol(-1) on the (100), (110) and (111) facets, respectively...
July 18, 2017: Physical Chemistry Chemical Physics: PCCP
Houshang Najafi, Zeynab Mohamadi Yarijani, Meysam Najafi
In this study, the antioxidant activity of crocin via experimental and theoretical methods was investigated. In order to induce oxidative stress, 30-min renal ischemia and 24-h reperfusion were used in male Wistar rats. Oxidative stress was assessed by measuring tissue malondialdehyde (MDA) and ferric reducing/antioxidant power (FRAP). The results showed that following ischemia/reperfusion, the level of MDA was increased and FRAP decreased. Both of these changes were alleviated by crocin administration. The bond dissociation enthalpy and ionization potential values as enthalpies of mechanism of antioxidant activity of crocin were calculated by density functional theory method...
July 17, 2017: Inflammation
Mirosław Chorążewski, Eugene B Postnikov, Bernadeta Jasiok, Yuriy V Nedyalkov, Johan Jacquemin
During this work, we demonstrate, for the first time, that the volumetric properties of pure ionic liquids could be truly predicted as a function of temperature from 219 K to 473 K and pressure up to 300 MPa. This has been achieved by using only density and isothermal compressibility data at atmospheric pressure through the Fluctuation Theory-based Tait-like Equation of State (FT-EoS). The experimental density data of 80 different ionic liquids, described in the literature by several research groups as a function of temperature and pressure, was then used to provide comparisons...
July 17, 2017: Scientific Reports
Gregory K Pierens, T K Venkatachalam, David C Reutens
A detailed NMR investigation of the chemical shifts of hydrogen and carbon atoms associated with the structure of the naturally occurring alkaloid colchicine was conducted using high field NMR. Initially, the experimental chemical shifts for colchicine in chloroform and DMSO were compared to the values calculated using density functional theory (DFT). There were significant deviations observed for the chloroform solvent, but these were only slight in the DMSO solution. Dilution of the chloroform solution changed the experimental chemical shifts and improved agreement with the DFT calculations, suggesting self-aggregation at higher concentrations...
July 17, 2017: Scientific Reports
Yi Zhang, Liangjie Fu, Zhan Shu, Huaming Yang, Aidong Tang, Tao Jiang
Substitutional doping is a strategy in which atomic impurities are optionally added to a host material to promote its properties, while the geometric and electronic structure evolution of natural nanoclay mineral upon substitutional metal doping is still ambiguous. This paper first designed an efficient lanthanum (La) doping strategy for nanotubular clay (halloysite nanotube, HNT) through the dynamic equilibrium of a substitutional atom in the presence of saturated AlCl3 solution, and systematic characterization of the samples was performed...
December 2017: Nanoscale Research Letters
A Ehsani, E Kowsari, F Boorboor Ajdari, R Safari, H Mohammad Shiri
In present work, for improving the electrochemical performance of conductive polymer, POAP/3-methyl-1-[2-(2-{2-[2-[(3-methyl-1-H-imidazol-3-ium-1-yl)ethoxy]ethoxy}-ethoxy)ethyl]-1-H-imidazol-3-ium dichloride (MIEID) composite films have been fabricated by poly ortho aminophenol (POAP) electropolymerization in the presence of MIEID as active electrodes for electrochemical supercapacitors. Different electrochemical methods including galvanostatic charge discharge experiments, cyclic voltammetry and electrochemical impedance spectroscopy have been applied to study the system performance...
July 3, 2017: Journal of Colloid and Interface Science
Hong-Ping Zhang, Jia-Liang Hou, Yaobin Wang, Ping-Ping Tang, Ya-Ping Zhang, Xiao-Yan Lin, Changsheng Liu, Youhong Tang
Polychlorinated dibenzo-p-dioxins (PCDDs) are highly toxic to humans. The search for novel and effective methods and materials for detecting or removing these gas pollutants is becoming more important and urgent. With its high specific surface area, abundance, and variety of potential applications, phosphorene has attracted much research interest. In this study, density functional theory was used to study the interactions between a doped phosphorene sheet and a tetrachlorodibenzo-p-dioxin (TCDD) molecule. The initial configurations of the TCDD and metallic (Ca or Ti) or nonmetallic (S and Se) dopants were investigated during the TCDD-phosphorene interaction study...
July 3, 2017: Chemosphere
Basant A Ali, Nageh K Allam
We report density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations on the widely used N3 dye (cis-[Ru(2,2'-bipyridine-4,4'-dicarboxylic acid)2(NCS)2] and its trans isomer with different π-spacers. The study compared the sensitization properties of the two isomers in terms of their electronic properties such as light harvesting efficiency (LHE), absorbed wavelength (λMax) and molecular orbital distribution. Also, charge transfer descriptors, such as the charge transfer distance (D(CT)), dipole moment (μ(CT)), and the amount of charge transferred (q(CT)) were investigated...
July 12, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Tingting You, Xiufeng Lang, Anping Huang, Penggang Yin
A computational study on aromatic dithiol derivatives (HS-Ar-X-Ar-SH, X=O, S, Se, NH, CH2, NN, CHCH, CC) interacting with gold cluster(s) was presented to investigate the chemical enhancement mechanism related to surface-enhanced Raman spectroscopy (SERS) for molecular junctions. Density functional theory (DFT) were performed on derivatives molecules as well as their single-end-linked (SEL) or double-end-linked (DEL) complexes for geometric, spectra, electronic and excitation properties, leading to discussions on dominant factor during SERS process...
July 12, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Alaaeldin M F Galal, Elsayed M Shalaby, Ahmed Abouelsayed, Medhat A Ibrahim, Emad Al-Ashkar, Atef G Hanna
The absolute configuration of 5-chloro-2-methoxy-N-phenylbenzamide single crystal [compound (1)] and the effect of introducing -[CH2]n-, n=1,2 group adjacent to the amide group [compounds (2) and (3)], were studied. Furthermore, the replacement of the methoxy group with a hydroxy group [compound (4)] was defined. Proton and carbon-13 NMR spectrometer were used to record the structural information of the prepared compounds. X-ray single crystal diffractometer were used to elucidate the 3D structural configurations...
July 4, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Miguel A Caro, Olga Lopez-Acevedo, Tomi Laurila
We present a complete methodology to consistently estimate redox potentials strictly from first principles, without any experimental input. The methodology is based on (i) ab initio molecular dynamics (MD) simulations, (ii) all-atom explicit solvation, (iii) the two-phase thermodynamic (2PT) model and (iv) the use of electrostatic potentials as references for the absolute electrochemical scale. We apply the approach presented to compute reduction potentials of the following redox couples: Cr(+2/+3), V(+2/+3), Ru(NH3)6(+2/+3), Sn(+2/+4), Cu(+1/+2), FcMeOH(0/+1) and Fe(+2/+3) (in aqueous solution) and Fc(0/+1) (in acetonitrile)...
July 17, 2017: Journal of Chemical Theory and Computation
Gaoxiang Liu, Sandra M Ciborowski, Kit Hansell Bowen
Pyridine-ligated gold cluster anions were studied through a combination of negative ion photoelectron spectroscopy and density functional theory calculations. Small gold cluster anions ligated by pyridine, Aun(py) were generated with a ligation cell coupled to a laser vaporization source (LVS). We showed that pyridine is weakly bound (physisorbed) to the Au2(-) moiety of Au2(py)(-) by interactions between its gold atoms and either the hydrogen atoms or the π-ring of pyridine. We also found that pyridine's lone electron pair strongly binds (chemisorbs) to both Au3(py)(-) and Au4(py)(-) through single gold atoms on each of these clusters...
July 17, 2017: Journal of Physical Chemistry. A
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