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https://www.readbyqxmd.com/read/28226221/development-of-new-density-functional-approximations
#1
Neil Qiang Su, Xin Xu
Kohn-Sham density functional theory has become the leading electronic structure method for atoms, molecules, and extended systems. It is in principle exact, but any practical application must rely on density functional approximations (DFAs) for the exchange-correlation energy. Here we emphasize four aspects of the subject: (a) philosophies and strategies for developing DFAs; (b) classification of DFAs; (c) major sources of error in existing DFAs; and (d) some recent developments and future directions. Expected final online publication date for the Annual Review of Physical Chemistry Volume 68 is April 20, 2017...
February 22, 2017: Annual Review of Physical Chemistry
https://www.readbyqxmd.com/read/28225625/spin-orbit-coupling-effects-on-ligand-free-icosahedral-matryoshka-superatoms
#2
Feiyun Long, Haitao Liu, Dafang Li, Jun Yan
With the help of density functional theory, a series of matryoshka superatoms $\rm{X@Y_{12}@X_{20}}$ (X=Ge, Y=Zn; X=Sn, Y=Mg, Mn, Zn or Cd; X=Pb, Y= Mg, Mn, Cd or Hg) with icosahedral symmetry has been extensively studied, to focus on the influence of the spin-orbit coupling on geometries, stabilities, electronic structures and magnetic moments for these clusters. Generally speaking, the effect of spin-orbit coupling is highly correlated with composition elements of these clusters. $\rm{Ge@Zn_{12}@Ge_{20}}$ is little affected by the spin-orbit coupling, while clusters containing Sn atom will generally undergo a moderate influence on their atomization energy, HOMO-LUMO gap and projected density of states...
February 22, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28225622/how-the-coordinated-structures-of-ag-i-catalysts-affect-the-outcomes-of-carbon-dioxide-incorporation-into-propargylic-amine-a-dft-study
#3
Ruming Yuan, Baohuan Wei, Gang Fu
Density functional theory calculations have been carried out to explore the detailed mechanisms for carbon dioxide incorporation of N-unsubstituted propargylic amine catalyzed by Ag(I) catalysts. We show that the reaction undergoes substrate adsorption or displacement, isomerization from amine-coordinated species to the alkyne-coordinated species, CO2 attack and proton transfer, giving the carbamate intermediate. Subsequently, the reaction would bifurcate at the intermolecular ring closing step, which produces five-membered ring (5MR) and six-membered ring (6MR) products at the same time, thus raising a regioselectivity issue...
February 22, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28225619/charge-transfer-induced-para-selective-sp2-c-h-bond-activation-of-arenes-by-use-of-a-hypervalent-iodine-compound-a-theoretical-study
#4
Jiyang Zhao, Shuhua Li
The reaction mechanism of the C-H bond activation of toluene promoted by the hypervalent iodine compound TIPP-I(OH)OTs was investigated in detail by density functional theory calculations. Our calculations show that a plausible reaction pathway of the C-H bond activation of toluene contains two stages: (1) the ligand exchange process on TIPP-I(OH)OTs, involving the substitution of the hydroxyl group and tosyloxyl group with TfOH; (2) the C-H bond activation of toluene promoted by the hypervalent iodine center with the assistance of the triflate anion...
February 22, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28225613/dehydrogenation-free-energy-of-co-2-aq-from-density-functional-theory-based-molecular-dynamics
#5
Florian H Hodel, Sandra Luber
Electron and proton transfers are important steps occurring in nature and in artificial (catalytic) reaction mechanisms. The often employed approach of calculating the energy differences of those steps using methods involving geometry optimizations neglects the influence of dynamic effects such as solvent rearrangement. To further investigate this issue and inspired by recent research in water oxidation, we calculate in the present study the dehydrogenation free energy of aqueous Co(2+), which is the free energy change associated with the first step of the reaction mechanism of model Co(II)-based water oxidation catalysts...
February 22, 2017: Journal of Chemical Theory and Computation
https://www.readbyqxmd.com/read/28225612/exciton-absorption-spectra-by-linear-response-methods-application-to-conjugated-polymers
#6
Martin A Mosquera, Nicholas E Jackson, Thomas J Fauvell, Matthew S J Kelley, Lin X Chen, George C Schatz, Mark A Ratner
The theoretical description of the time-evolution of excitons requires, as an initial step, the calculation of their spectra, which has been inaccessible to most users due to the high computational scaling of conventional algorithms, and accuracy issues caused by common density functionals. Previously (J. Chem. Phys., 2016, 144, 204105) we developed a simple method that resolves these issues. Our scheme is based on a two-step calculation in which a linear-response TDDFT calculation is used to generate orbitals perturbed by the excitonic state, and then a second linear-response TDDFT calculation is used to determine the spectrum of excitations relative to the excitonic state...
February 22, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28225605/electrostatic-control-of-regioselectivity-in-au-i-catalyzed-hydroarylation
#7
Vivian M Lau, William C Pfalzgraff, Thomas E Markland, Matthew W Kanan
Competing pathways in catalytic reactions often involve transition states with very different charge distributions, but this difference is rarely exploited to control selectivity. The proximity of a counterion to a charged catalyst in an ion paired complex gives rise to strong electrostatic interactions that could be used to energetically differentiate transition states. Here we investigate the effects of ion pairing on the regioselectivity of the hydroarylation of 3-substituted phenyl propargyl ethers catalyzed by cationic Au(I) complexes, which forms a mixture of 5- and 7-substituted 2H-chromenes...
February 22, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28225252/luminescent-re-i-carbonyl-complexes-as-trackable-photocorms-for-co-delivery-to-cellular-targets
#8
Indranil Chakraborty, Jorge Jimenez, W M C Sameera, Masako Kato, Pradip K Mascharak
A family of Re(I) carbonyl complexes of general formula [ReX(CO)3(phen)](0/1+) (where X = Cl(-), CF3SO3(-), MeCN, PPh3, and methylimidazole) derived from 1,10-phenanthroline (phen) exhibits variable emission characteristics depending on the presence of the sixth ancillary ligand/group (X). All complexes but with X = MeCN exhibit moderate CO release upon irradiation with low-power UV light and are indefinitely stable in anaerobic/aerobic environment in solution as well as in solid state when kept under dark condition...
February 22, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28225197/prediction-on-dielectric-strength-and-boiling-point-of-gaseous-molecules-for-replacement-of-sf6
#9
Xiaojuan Yu, Hua Hou, Baoshan Wang
Developing the environment-friendly insulation gases to replace sulfur hexafluoride (SF6 ) has attracted considerable experimental and theoretical attentions but without success. A computational methodology was presented herein for prediction on dielectric strength and boiling point of arbitrary gaseous molecules in the purpose of molecular design and screening. New structure-activity relationship (SAR) models have been established by combining the density-dependent properties of the electrostatic potential surface, including surface area and the statistical variance of the surface potentials, with the molecular properties including polarizability, electronegativity, and hardness...
April 15, 2017: Journal of Computational Chemistry
https://www.readbyqxmd.com/read/28225121/the-local-electronic-properties-of-individual-pt-atoms-adsorbed-on-tio2-110-studied-by-kelvin-probe-force-microscopy-and-first-principles-simulations
#10
Ayhan Yurtsever, Delia Fernández-Torre, Jo Onoda, Masayuki Abe, Seizo Morita, Yoshiaki Sugimoto, Rubén Pérez
Noble metal nanostructures dispersed on metal oxide surfaces have applications in diverse areas such as catalysis, chemical sensing, and energy harvesting. Their reactivity, chemical selectivity, stability, and light absorption properties are controlled by the interactions at the metal/oxide interface. Single-atom metal adsorbates on the rutile TiO2(110)-(1 × 1) surface have become a paradigmatic model to characterize those interactions and to understand the unique electronic properties of these supported nanostructures...
February 22, 2017: Nanoscale
https://www.readbyqxmd.com/read/28225110/tuning-the-hydrogen-evolution-activity-of-%C3%AE-mo2c-nanoparticles-via-control-of-their-growth-conditions
#11
Timothy T Yang, Wissam A Saidi
The use of water electrocatalysis for hydrogen production is a promising, sustainable and greenhouse-gas-free process to develop disruptive renewable energy technologies. Transition metal carbides, in particular β-phase Mo2C, are garnering increased attention as hydrogen evolution reaction (HER) catalysts due to their favourable synthesis conditions, stability and high catalytic efficiency. We use a thermodynamic approach in conjunction with density functional theory and a kinetic model of exchange current density to systematically study the HER activity of β-Mo2C under different experimental conditions...
February 22, 2017: Nanoscale
https://www.readbyqxmd.com/read/28222257/an-iron-ii-ylide-complex-as-a-masked-open-shell-iron-alkylidene-species-in-its-alkylidene-transfer-reactions-with-alkenes
#12
Jian Liu, Lianrui Hu, Lei Wang, Hui Chen, Liang Deng
Transition-metal alkylidenes are important reactive organometallic intermediates, and our current knowledge on them has been mainly restricted to those with closed-shell electronic configurations. In this study, we present the exploration on open-shell iron alkylidenes with a weak-field tripodal amido-phosphine-amido ligand. We found that a high-spin (amido-phosphine-amido)iron(II) complex can react with (p-tolyl)2CN2 to afford a high-spin (amido-ylide-amido)iron(II) complex, 2, which could transfer its alkylidene moiety to a variety of alkenes, either the electron-rich or electron-deficient ones, to form cyclopropane derivatives...
February 21, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28221386/searching-for-large-gap-quantum-spin-hall-insulators-boron-nitride-pb-sn-%C3%AE-al2o3-sandwich-structures
#13
Hui Wang, D Lu, J Kim, Z Wang, S T Pi, R Q Wu
Topological insulators hold great potential for efficient information processing and storage. Using density functional theory calculations, we predict that a honeycomb lead monolayer can be stabilized on an Al2O3 (0001) substrate to become topologically non-trivial with a sizeable band gap (∼0.27 eV). Furthermore, we propose to use a hexagonal boron-nitride (h-BN) monolayer as a protection for the topological states of Pb/Al2O3 and Sn/Al2O3. Our findings suggest new possibilities for designing and protecting two-dimensional TIs for practical applications...
February 21, 2017: Nanoscale
https://www.readbyqxmd.com/read/28221360/why-copper-is-preferred-over-iron-for-oxygen-activation-and-reduction-in-haem-copper-oxidases
#14
Ambika Bhagi-Damodaran, Matthew A Michael, Qianhong Zhu, Julian Reed, Braddock A Sandoval, Evan N Mirts, Saumen Chakraborty, Pierre Moënne-Loccoz, Yong Zhang, Yi Lu
Haem-copper oxidase (HCO) catalyses the natural reduction of oxygen to water using a haem-copper centre. Despite decades of research on HCOs, the role of non-haem metal and the reason for nature's choice of copper over other metals such as iron remains unclear. Here, we use a biosynthetic model of HCO in myoglobin that selectively binds different non-haem metals to demonstrate 30-fold and 11-fold enhancements in the oxidase activity of Cu- and Fe-bound HCO mimics, respectively, as compared with Zn-bound mimics...
March 2017: Nature Chemistry
https://www.readbyqxmd.com/read/28220847/atomic-layer-confined-vacancies-for-atomic-level-insights-into-carbon-dioxide-electroreduction
#15
Shan Gao, Zhongti Sun, Wei Liu, Xingchen Jiao, Xiaolong Zu, Qitao Hu, Yongfu Sun, Tao Yao, Wenhua Zhang, Shiqiang Wei, Yi Xie
The role of oxygen vacancies in carbon dioxide electroreduction remains somewhat unclear. Here we construct a model of oxygen vacancies confined in atomic layer, taking the synthetic oxygen-deficient cobalt oxide single-unit-cell layers as an example. Density functional theory calculations demonstrate the main defect is the oxygen(II) vacancy, while X-ray absorption fine structure spectroscopy reveals their distinct oxygen vacancy concentrations. Proton transfer is theoretically/experimentally demonstrated to be a rate-limiting step, while energy calculations unveil that the presence of oxygen(II) vacancies lower the rate-limiting activation barrier from 0...
February 21, 2017: Nature Communications
https://www.readbyqxmd.com/read/28220334/future-directions-in-personality-occupational-and-medical-selection-myths-misunderstandings-measurement-and-suggestions
#16
Eamonn Ferguson, Filip Lievens
This paper has two objectives: (1) presenting recent advances in personality theory whereby personality traits are conceptualized within a framework that focuses on the dynamic interactions of behaviour, biology, context, and states, and (2) discussing the implications of these developments for measurement and medical selection. We start by presenting evidence that traits are no longer regarded as stable deterministic predictors of behaviour. Instead, traits are found to change across generations, the life span, and in response to environmental contingencies...
February 20, 2017: Advances in Health Sciences Education: Theory and Practice
https://www.readbyqxmd.com/read/28220171/towards-highly-active-pd-ceo2-for-alkene-hydrogenation-by-tuning-pd-dispersion-and-surface-properties-of-the-catalysts
#17
Sai Zhang, Jing Li, Zhaoming Xia, Chao Wu, Zhiyun Zhang, Yuanyuan Ma, Yongquan Qu
Extensive applications of noble metals as heterogeneous catalysts are limited by their global reserve scarcity and exorbitant price. Identifying the intrinsic active nature of a catalyst benefits the designing of catalysts with trace amounts of noble metals; these catalysts display better or comparable overall catalytic efficiency than their heavily loaded counterparts. Herein, systematic studies on Pd dispersion and surface properties of a series of Pd/CeO2 catalysts for styrene hydrogenation showed that high Pd dispersion and surface abundant defects of the catalysts are essential to realize superior activity...
February 21, 2017: Nanoscale
https://www.readbyqxmd.com/read/28220165/new-insights-into-the-electroreduction-of-ethylene-sulfite-as-an-electrolyte-additive-for-facilitating-solid-electrolyte-interphase-formation-in-lithium-ion-batteries
#18
Youmin Sun, Yixuan Wang
To help understand the solid electrolyte interphase (SEI) formation facilitated by electrolyte additives of lithium-ion batteries (LIBs) the supermolecular clusters [(ES)Li(+)(PC)m](PC)n (m = 1-2; n = 0, 6 and 9) were used to investigate the electroreductive decompositions of the electrolyte additive ethylene sulfite (ES) as well as the solvent propylene carbonate (PC) with density functional theory. The results show that ES can be reduced prior to PC, resulting in a reduction precursor that will then undergo a ring opening decomposition to yield a radical anion...
February 21, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28219039/microwave-dielectric-relaxation-spectroscopy-study-of-propylene-glycol-ethanol-binary-mixtures-temperature-dependence
#19
T Vishwam, Suriya Shihab, V R K Murthy, Ha Sie Tiong, S Sreehari Sastry
Complex dielectric permittivity measurements of propylene glycol (PG) in ethanol at various mole fractions were measured by using open-ended coaxial probe technique at different temperatures in the frequency range 0.02<ν/GHz<20. The dipole moment (μ), excess dipole moment (Δμ),excess permittivity (ε(E)), excess inverse relaxation time(1/τ)(E), Bruggeman parameter (fB), excess Helmholtz energy (ΔF(E)) are determined using experimental data. From the minimum energy based geometry optimization, dipole moments of individual monomers of propylene glycol and ethanol and their binary system have been evaluated theoretically at gaseous state as well as alcoholic medium by using PCM and IEFPCM solvation models from the Hatree-Fock (HF) and Density Functional Theory (DFT-B3LYP) methods with 6-311G* and 6-311G** basis sets...
February 11, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
https://www.readbyqxmd.com/read/28218893/dopant-activation-mechanism-of-bi-wire-%C3%AE-doping-into-si-crystal-investigated-with-wavelength-dispersive-%C3%AF-uorescence-x-ray-absorption-%C3%AF-ne-structure-and-density-functional-theory
#20
Koichi Murata, Christopher Kirkham, Masaru Shimomura, Kiyofumi Nitta, Tomoya Uruga, Yasuko Terada, Koh-Ichi Nittoh, David Bowler, Kazushi Miki
We successfully characterized the local structures of Bi atoms in a wire-δ-doped layer (1/8 ML) in a Si crystal, using wavelength dispersive fluorescence X-ray absorption fine structure at the beamline BL37XU, in SPring-8, with the help of density functional theory calculations. It was found that the burial of Bi nanolines on the Si(001) surface, via growth of Si capping layer at 400°C by molecular beam epitaxy, reduced the Bi-Si bond length from 2.79 ± 0.01 Å to 2.63 ± 0.02 Å. We infer that following epitaxial growth the Bi-Bi dimers of the nanoline are broken, and the Bi atoms are located at substitutional sites within the Si crystal, leading to the shorter Bi-Si bond lengths...
February 20, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
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