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density functional theory

Junping Zhang, Jianjun Liao, Fan Yang, Ming Xu, Shiwei Lin
Three non-metallic elements, sulfur, fluorine, and iodine, were used to dope the ultrathin two-dimensional TiO₂ nanosheets, which would regulate their electroanalytical properties toward heavy metal ions. Among these doped materials, fluorine-doped TiO₂ nanosheets shows the highest electrochemical sensitivity and a superior detection limit toward Pb(II) when the doping concentration is 10%. When compared with the bare TiO₂ nanosheets, the sensitivity increased by 102%, and the detection limit decreased by 36...
October 14, 2017: Nanomaterials
Elizabeth Nichols, Viviana Alarcón, Shaun Forgie, Luis A Gomez-Puerta, Matthew S Jones
A diversity of macro- and microparasitic species exert strong influences on wildlife population density, community structure, and ecosystem functioning, all through their impacts on individual host fitness. Through consuming, manipulating, and relocating wildlife feces, over 7,000 species of coprophagous dung beetles interact with a staggering diversity of wildlife parasites with fecal-oral transmission in ways that both increase and decrease transmission. Here, we review the mechanisms by which dung beetles influence micro- and macroparasite transmission and outline a future research framework that integrates theory and empirical insights to advance our understanding of how these relationships may interact with ongoing environmental change drivers to further influence wildlife populations and community structure...
September 28, 2017: ILAR Journal
Liping Fang, Qiantao Shi, Jessica Nguyen, Baile Wu, Zimeng Wang, Irene M C Lo
Lanthanum-based materials are effective for sequestering phosphate in water, however their removal mechanisms remain unclear, and the effects of environmentally relevant factors have not yet been studied. Hereby, this study explored the mechanisms of phosphate removal using La(OH)3 by employing extended X-ray absorption spectroscopy (EXAFS), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), density functional theory (DFT) and chemical equilibrium modeling. The results showed that surface complexation was the primary mechanism for phosphate removal and in binary phosphate configurations, namely diprotonated bidentate mononuclear (BM-H2) and bidentate binuclear (BB-H2), coexisting on La(OH)3 in acidic conditions...
October 16, 2017: Environmental Science & Technology
Stefan Holler, Michael Tüchler, Michaela C Roschger, Ferdinand Belaj, Luis F Veiros, Karl Kirchner, Nadia C Mösch-Zanetti
A novel selenium-containing pyridazinyl-based soft scorpionate ligand (KTnse) was synthesized. It reacts with CoCl2 and NiCl2, yielding the first metallaboratrane complexes with selenium in their donor positions. Further substitution with Ag(OTf) or NaN3 allows isolation of the respective triflate or azide complexes. Reaction with Ag(OTf) leads in the case of nickel to a dinuclear, dicationic complex with a short Ni-Ni distance, while cobalt gave a mononuclear cationic species. Substitution of the chloride by azide yields with both metals the respective azide complexes...
October 16, 2017: Inorganic Chemistry
Juanjuan Gao, Jingkun Fang, Xuehai Ju, Weiqing Zhu, Xuezhen Lin, Shupeng Zhang, Chuang Ma, Haiou Song
An electrochemically active sensing nanomaterial (denoted as CD-MPEA-NG) has been successfully constructed by an hierarchical self-assembly of cyclodextrin (CD) and N, N-dimethyl-4-(phenylethynyl)aniline (MPEA) on N-doped graphene (NG) in a low-temperature hydrothermal process. The unique nanostructure of the high-performance CD-MPEA-NG was confirmed by utilizing the Fourier transform infrared spectra, an X-ray diffractometer, a differential pulse voltammetry (DPV), etc. In particular, the method of density functional theory with dispersion energy (DFT-D) of wB97XD/LanL2DZ was employed to optimize and describe the face-to-face packing structure of heterodimers of NG and MPEA...
October 16, 2017: ACS Applied Materials & Interfaces
Francisco de Santiago, Alejandro Trejo, Alvaro Miranda, Eliel Carvajal, Luis Antonio Pérez, Miguel Cruz-Irisson
In this work, we address the effects of molecular doping on the electronic properties of fluorinated and chlorinated silicon nanowires (SiNWs), in comparison with those corresponding to hydrogen-passivated SiNWs. Adsorption of n-type dopant molecules on hydrogenated and halogenated SiNWs and their chemisorption energies, formation energies, and electronic band gap are studied by using density functional theory calculations. The results show that there are considerable charge transfers and strong covalent interactions between the dopant molecules and the SiNWs...
October 16, 2017: Journal of Molecular Modeling
Plamen P Angelov, Xiaowei Gu, Jose C Pr
Based on a critical analysis of data analytics and its foundations, we propose a functional approach to estimate data ensemble properties, which is based entirely on the empirical observations of discrete data samples and the relative proximity of these points in the data space and hence named empirical data analysis (EDA). The ensemble functions include the nonparametric square centrality (a measure of closeness used in graph theory) and typicality (an empirically derived quantity which resembles probability)...
October 12, 2017: IEEE Transactions on Cybernetics
Alexander T Taguchi, Patrick J O'Malley, Colin A Wraight, Sergei A Dikanov
Determining the complete electron spin density distribution for protein-bound radicals, even with advanced pulsed electron paramagnetic resonance (EPR) methods, is a formidable task. Here we present a strategy to overcome this problem combining multi-frequency HYSCORE and ENDOR measurements on site-specifically (13)C-labeled samples with DFT calculations on model systems. As a demonstration of this approach, pulsed EPR experiments are performed on the primary QA and secondary QB ubisemiquinones of the photosynthetic reaction center from Rhodobacter sphaeroides (13)C-labeled at the ring and tail positions...
October 16, 2017: Journal of Physical Chemistry. B
Rubha Ponraj, Aravindaraj Govindaraj Kannan, Jun Hwan Ahn, Jae Hee Lee, Joonhee Kang, Byungchan Han, Dong-Won Kim
The critical issues that hinder the practical applications of lithium-sulfur batteries, such as dissolution and migration of lithium polysulfides, poor electronic conductivity of sulfur and its discharge products and low loading of sulfur, have been addressed by designing a functional separator modified using hydroxyl-functionalized carbon nanotubes (CNTOH). Density functional theory (DFT) calculations and experimental results demonstrate that the hydroxyl groups in the CNTOH provoked strong interaction with lithium polysulfides and resulted in effective trapping of lithium polysulfides within the sulfur cathode side...
October 16, 2017: ACS Applied Materials & Interfaces
Runzhang Xu, Bilu Liu, Xiaolong Zou, Hui-Ming Cheng
Recent development of two-dimensional transition-metal dichalcogenides in electronics and optoelelectronics has triggered the exploration in spintronics, with high demand in search for half-metallicity in these systems. Here, through density functional theory (DFT) calculations, we predict robust half-metallic behaviors in Co edge-doped WSe2 nanoribbons. With electrons partially occupying the anti-bonding state consisting of Co 3dyz and Se 4pz orbitals, the system becomes spin-polarized due to the defect-state induced Stoner effect, and the strong exchange splitting eventually gives rise to the half-metallicity...
October 16, 2017: ACS Applied Materials & Interfaces
Francesc Viñes, Gerasimos Konstantatos, Francesc Illas
The influence of cationic disorder on the electronic structure of ternary compounds, here exemplified on AgBiS2 material, is studied by means of accurate first principles periodic density functional theory based calculations. For AgBiS2 cationic disorder in going from semiconducting matildite to a metallic arrangement crystal structure is found to induce a significant decrease in the band gap, as a result of cation-disorder conduction band tail states penetrating into the matildite bandgap. Properly aligned conduction band minimum and valence band maximum show that cationic disorders lead to a noticeable drop of the former and a slight increase of the latter...
October 16, 2017: Physical Chemistry Chemical Physics: PCCP
Li Gong, Jie-Jie Chen, Yang Mu
Converting CO2 into valuable chemicals and fuels is one of the most practical routes for reducing CO2 emissions while fossil fuels continue to dominate the energy sector. Noble-metal-free NiFe bimetal nanoparticles have shown good catalytic activity in CO2 conversion. Herein we theoretically evaluated the catalytic performance and possible mechanisms of NiFe-based nanoclusters for hydrogenating CO2 to form formic acid and CO through bicarbonate by using a periodic and self-consistent density functional theory (DFT) simulation...
October 16, 2017: Physical Chemistry Chemical Physics: PCCP
Amrita Pal, Lai Kai Wen, Chia Yao Jun, Il Jeon, Yutaka Matsuo, Sergei Manzhos
We present a systematic comparative density functional theory-density functional tight binding study of multiple derivatives of C60 and C70 with different addends, in molecular as well as solid state. In particular, effects due to fullerene size, type and number of addends, and of crystallinity on band structure, charge transport, and optical properties are investigated. These are important, in particular, for rational selection of fullerene derivatives as acceptor and electron transport layers in organic as well as planar inverted perovskite solar cells...
October 16, 2017: Physical Chemistry Chemical Physics: PCCP
Shuanhu Qi, Friederike Schmid
We present a multiscale hybrid particle-field scheme for the simulation of relaxation and diffusion behavior of soft condensed matter systems. It combines particle-based Brownian dynamics and field-based local dynamics in an adaptive sense such that particles can switch their level of resolution on the fly. The switching of resolution is controlled by a tuning function which can be chosen at will according to the geometry of the system. As an application, the hybrid scheme is used to study the kinetics of interfacial broadening of a polymer blend, and is validated by comparing the results to the predictions from pure Brownian dynamics and pure local dynamics calculations...
October 16, 2017: Soft Matter
Francis Opoku, Krishna Kuben Govender, Cornelia Gertina Catharina Elizabeth van Sittert, Penny Poomani Govender
In the 21st century, the growing demand of global energy is one of the key challenges. The photocatalytic generation of hydrogen has attracted extensive attention to discuss the increasing global demand for sustainable and clean energy. However, hydrogen evolution reactions normally use the economically expensive rare noble metals and the processes remain a challenge. Herein, low-cost BiNbO4/MWO4(010) heterostructures are studied for the first time to check their suitability towards photocatalytic hydrogen production...
October 16, 2017: Physical Chemistry Chemical Physics: PCCP
Gongli Ma, Guoliang Song, Zhen Hua Li
A strategy for the reduction of CO2 to CO by or catalyzed by metal-free silylboranes has been proposed with the aid of density functional theory (DFT) computations. We showed that one oxygen atom of CO2 can be abstracted by silylboranes without catalysts or by diboranes in the presence of silylborane catalysts with surprisingly low free-energy barriers so that the reaction can be realized under mild experimental conditions. To achieve this, the reduction mechanism of CO2 by a hierarchy of silylboranes (R1)2BSi(R2)3 was systematically investigated...
October 16, 2017: Physical Chemistry Chemical Physics: PCCP
Martin Setvin, Xiao Shi, Jan Hulva, Thomas Simschitz, Gareth S Parkinson, Michael Schmid, Cristiana Di Valentin, Annabella Selloni, Ulrike Diebold
The photoactivity of methanol adsorbed on the anatase TiO2 (101) surface was studied by a combination of scanning tunneling microscopy (STM), temperature-programmed desorption (TPD), X-ray photoemission spectroscopy (XPS), and density functional theory (DFT) calculations. Isolated methanol molecules adsorbed at the anatase (101) surface show a negligible photoactivity. Two ways of methanol activation were found. First, methoxy groups formed by reaction of methanol with coadsorbed O2 molecules or terminal OH groups are photoactive, and they turn into formaldehyde upon UV illumination...
October 6, 2017: ACS Catalysis
Yingju Yang, Jing Liu, Feng Liu, Zhen Wang, Sen Miao
Natural pyrite (FeS2) has been regarded as a kind of potential sorbents to control mercury emission from coal-fired power plants because of its low cost and high affinity between mercury and FeS2. Theoretical investigations based on density functional theory (DFT) were carried out to discern mercury adsorption, reaction and desorption mechanisms over pyrite surface. DFT calculation results indicate that Hg(0) adsorption on FeS2(100) and FeS2(110) surfaces is dominated by physisorption and chemisorption mechanisms, respectively...
October 7, 2017: Journal of Hazardous Materials
Elahe K Astani, Nai-Chi Chen, Yen-Chieh Huang, Aidin Bahrami, Li-Ying Chen, Pei-Ru Lin, Hong-Hsiang Guan, Chien-Chih Lin, Phimonphan Chuankhayan, Nasser L Hadipour, Chun-Jung Chen
Crystal structure of the protrusion domain (P-domain) of the grouper nervous necrosis virus (GNNV) shows the presence of three-fold trimeric protrusions with two asymmetrical calcium cations along the non-crystallographic three-fold axis. The trimeric interaction natures of the interacting residues and the calcium cations with the neighboring residues within the trimeric interface have been studied by the quantum theory of atoms in molecules (QTAIM) and natural bond orbital (NBO) analyses in the framework of the density-functional theory (DFT) approach...
October 3, 2017: Journal of Molecular Graphics & Modelling
Tobias Fahleson, Patrick Norman
The second-order nonlinear (or cubic) response function is derived from the Ehrenfest theorem with inclusion made of the finite lifetimes of the excited states, representing the extension of the derivation of the quadratic response function in the same framework [P. Norman et al., J. Chem. Phys. 123, 194103 (2005)]. The resulting damped response functions are physically sound and converging also in near-resonance and resonance regions of the spectrum. Being an accurate approximation for small complex frequencies (defined as the sum of an optical frequency and an imaginary damping parameter), the polynomial expansion of the complex cubic response function in terms of the said frequencies is presented and used to validate the program implementation...
October 14, 2017: Journal of Chemical Physics
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