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density functional theory

K Nejati, A Hosseinian, A Bekhradnia, E Vessally, L Edjlali
It has been recently indicated that the Li-ion batteries may be replaced by Na-ion batteries because of their low safety, high cost, and low-temperature performance, and lack of the Li mineral reserves. Here, using density functional theory calculations, we studied the potential application of B12N12 nanoclusters as anode in Na-ion batteries. Our calculations indicate that the adsorption energy of Na(+) and Na are about -23.4 and -1.4kcal/mol, respectively, and the pristine BN cage to improve suffers from a low cell voltage (∼0...
March 6, 2017: Journal of Molecular Graphics & Modelling
Lin Cheng, Xiaojuan Yu, Kun Zhao, Hua Hou, Baoshan Wang
Electronic structures of Trifluoromethyl imionosulfur difluoride (CF3NSF2) and degradation mechanisms by hydroxyl radical have been investigated using density functional theory (M06-2X), the complete basis set quadratic CBS-Q, and the explicitly correlated coupled-cluster methods [CCSD(T)-F12]. The d-function augmented Correlation-consistent basis sets including triple- and quadruple- were employed for the sulfur-containing species. It was found that CF3NSF2 exists as two conformations connected by the internal rotation of CF3 around the central NS bond...
March 21, 2017: Journal of Physical Chemistry. A
Martin K Schmitt, Oliver Janka, Oliver Niehaus, Thomas Dresselhaus, Rainer Pöttgen, Florian Pielnhofer, Richard Weihrich, Maria Krzhizhanovskaya, Stanislav Filatov, Rimma Bubnova, Lkhamsuren Bayarjargal, Björn Winkler, Robert Glaum, Hubert Huppertz
γ-NiB4O7 was synthesized in a high-pressure/high-temperature experiment at 5 GPa and 900 °C. The single-crystal structure analysis yielded the following results: space group P6522 (No. 179), a = 425.6(2), c = 3490.5(2) pm, V = 0.5475(2) nm(3), Z = 6, and Flack parameter x = -0.010(5). Second harmonic generation measurements confirmed the acentric crystal structure. Furthermore, γ-NiB4O7 was characterized via vibrational as well as single-crystal electronic absorption spectroscopy, magnetic measurements, high-temperature X-ray diffraction, differential scanning calorimetry, and thermogravimetry...
March 21, 2017: Inorganic Chemistry
Mehri Javan Khoshkholgh, Mohammad Reza Abolhassani, Farah Marsusi
This paper studies donor-acceptor systems which incorporate benzodithiophene (BDT), benzodifuran (BDF) and benzodipyrrole (BDP) units as the electron-rich monomer with TT unit representing the electron-deficient monomer. This research is based on employing density functional theory (DFT) and time-dependent DFT (TD-DFT). The highest occupied molecular orbitals (HOMO) and the lowest unoccupied molecular orbitals (LUMO), HOMO-LUMO gaps and dihedral-angles of these copolymers were calculated using oligomer extrapolation technique and periodic boundary condition (PBC) method...
March 7, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Jie Guan, Hsun-Jen Chuang, Zhixian Zhou, David Tomanek
In search of an improved strategy to form low-resistance contacts to semiconducting transition metal dichalcogenides, we combine ab initio density functional electronic structure calculations for an NbSe2/WSe2 interface with quantum transport measurements of the corresponding heterojunction between a few-layer WSe2 semiconductor and a metallic NbSe2 layer. Our theoretical results suggest that, besides a rigid band shift associated with charge transfer, the presence of NbSe2 does not modify the electronic structure of WSe2...
March 20, 2017: ACS Nano
Song Liu, Adri C T van Duin, Diana M van Duin, Bin Liu, James H Edgar
Atomistic-scale insights into the growth of a continuous, atomically thin hexagonal boron nitride (hBN) lattice from elemental boron and nitrogen on Ni substrates were obtained from multi-scale modeling combining density functional theory (DFT) and reactive molecular dynamics (rMD). The quantum mechanical calculations focused on the adsorption and reaction energetics for the hBN building-block species, i.e., atomic B, N, BxNy (x, y = 1-2), on Ni(111) and Ni(211), and the diffusion pathways of elemental B and N on these slab model surfaces and in the sublayer...
March 20, 2017: ACS Nano
Masae Takahashi, Nubuyuki Okamura, Xinyi Fan, Hitoshi Shirakawa, Hiroaki Minamide
We have investigated the terahertz-spectral property of nicotinamide focusing on the temperature dependence in the range of 14 to 300 K. We observed that almost all peaks in the terahertz spectrum of the nicotinamide crystal showed a remarkable shift with temperature, whereas the lowest-frequency peak at 34.8 cm-1 showed a negligible shift with temperature. By analyzing the terahertz spectrum with the dispersion-corrected density-functional-theory calculations, we found that the difference in the temperature dependence of the peak shift is well understood in terms of the presence/absence of stretching vibration of the intermolecular hydrogen bond in the mode and the change of cell parameters...
March 20, 2017: Journal of Physical Chemistry. A
Cai-Rong Zhang, Xing-Yu Li, Yu-Lin Shen, Youzhi Wu, Zi-Jiang Liu, Hongshan Chen
Novel dye sensitizers are highly expected in the development of dye-sensitized solar cells (DSSCs) since dye sensitizers can significantly affect the power conversion efficiency (PCE). Here, the molecular docking strategy is applied to design panchromatic dye sensitizers for DSSCs in order to improve light-harvesting efficiency covering the full solar spectrum. Considering the broad absorption bands of tetraanthracenylporphyrins (TAnPs) and tetraazuleneporphyrins (TAzPs), based upon porphyrin dye sensitizer YD2-o-C8, the panchromatic dye sensitizers coded as H2(TAnP)-α, H2(TAzP)-γ, H2(TAzP)-ε, and H2(TAzP)-δ are designed by the substitution of the porphyrin-ring in YD2-o-C8 with TAnPs and TAzPs moieties at different positions...
March 20, 2017: Journal of Physical Chemistry. A
Matthew N Grayson
We report density functional theory calculations which examine the mechanism and origins of stereoselectivity of Soós' landmark discovery from 2005 that cinchona thioureas catalyze the asymmetric Michael addition of nitroalkanes to enones. We show that the electrophile is activated by the catalyst's protonated amine and that the nucleophile binds to the thiourea moiety by hydrogen bonding. These results lead to the correction of published mechanistic work which did not consider this activation mode. We have also investigated the corresponding cinchona squaramide-catalyzed reaction and found that it proceeds by the same mechanism, despite the differences in the geometry of the two catalysts' hydrogen bond donating groups, which demonstrates the generality of this mechanistic model...
March 20, 2017: Journal of Organic Chemistry
Benoît Boucher, Rabih Al Rahal Al Orabi, Bruno Fontaine, Yuri Grin, Régis Gautier, Jean-François Halet
The possible existence of group 6 TM3 compounds with T = Cr, Mo, W and M = Ga, In is investigated with the aid of density functional theory calculations. Their most probable crystal structure is expected to be of the FeGa3 type tetragonal space group P42/mnm. All compounds are computed to be semiconductors with a band gap ranging from 0.08 to 0.43 eV, at the modified Becke-Johnson level of theory. The thermoelectric properties are analyzed via calculations based on Boltzmann transport equation under a constant relaxation time approximation...
March 20, 2017: Inorganic Chemistry
Michael Lesslie, John T Lawler, Andy Dang, Joseph A Korn, Daniel Bim, Vincent Steinmetz, Philippe Maitre, Frantisek Turecek, Victor Ryzhov
The radical cation of cytosine (Cyt*+) was generated via dissociative oxidation from a ternary Cu(II) complex in the gas phase. The radical cation was characterized by infrared multiple photon dissociation (IRMPD) spectroscopy in the fingerprint region, UV-VIS photodissociation (UV-PD), ion-molecule reactions, and theoretical calculations (density functional theory and ab initio). The IRMPD experimental spectrum has diagnostic bands for two enol/amino and two keto/amino tautomers of Cyt*+, that were calculated to be among the lowest-energy isomers in concert with a previous work (J...
March 20, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Yangmei Chen, Hua Y Geng, Xiaozhen Yan, Yi Sun, Qiang Wu, Xiangrong Chen
Hydrogen-rich compounds are important for understanding the dissociation of dense molecular hydrogen, as well as searching for room temperature Bardeen-Cooper-Schrieffer (BCS) superconductors. A recent high pressure experiment reported the successful synthesis of novel insulating lithium polyhydrides above 130 GPa. However, the results are in sharp contrast to a previous theoretical prediction by the PBE functional that around this pressure range all lithium polyhydrides (LiHn (n = 2-8)) should be metallic...
March 20, 2017: Inorganic Chemistry
Haldun Sevincli
The critical points and the corresponding singularities in the density of states of crystals were first classified by Van Hove with respect to their dimensionality and energy-momentum dispersions. Here, different from saddle-point Van Hove singularities, the occurrence of a continuum of critical points, which give rise to strong singularities in two-dimensional elemental hexagonal lattices, is shown using a minimal tight-binding formalism. The model predicts quartic energy-momentum dispersions in spite of quadratic or linear ones, which is also the origin of the strong singularity...
March 20, 2017: Nano Letters
Kunduchi Periya Vijayalakshmi, Cherumuttathu H Suresh
Cluster formation of ammonia borane (NH3BH3) driven by non-covalent H...H dihydrogen interaction is investigated at M06L/6-311+G(d,p) level density functional theory. For clusters containing up to six monomers, ladder, cyclic, stacked, cross-stacked, end-on, mixed and hexagonal configurations have been screened for their energetic stability. In the dimer, 7.94 kcal/mol stabilization energy per monomer (E(m)) is observed. Compared to ladder and cyclic configurations, a tetramer consisting of stacked dimer units is more stable by 3...
March 20, 2017: Journal of Physical Chemistry. A
Pablo Jiménez-Lozano, Albert Solé-Daura, Georges Wipff, Josep M Poblet, Alain Chaumont, Jorge J Carbó
The mechanism by which Zr-substituted and other transition metal-substituted polyoxometalates (POMs) form covalently linked dimers has been analyzed by means of static density functional theory (DFT) calculations with a continuous solvent model as well as Car-Parrinello molecular dynamics (CPMD) simulations with explicit solvent molecules. The study includes different stages of the process: the formation of the active species by alkalination of the solution and formation of intercluster linkages. CPMD simulations show that the Zr-triaqua precursor, [W5O18Zr(H2O)3](2-), under basic conditions, reacts with hydroxide anions to form Zr-aqua-hydroxo active species, [W5O18Zr(OH)(H2O)](3-)...
March 20, 2017: Inorganic Chemistry
Jincheng Lei, Yaowu Hu, Zishun Liu, Gary J Cheng, Kejie Zhao
Mixed results were reported on the anticorrosion of graphene coated metal surfaces - while graphene serves as an effective short-term barrier against corrosion and oxidation due to its low permeability to gases, the galvanic cell between graphene and metal substrate facilitates extensive corrosion in the long run. Defects in the graphene layer provide pathways for the permeation of oxidizing species. We study the role of defects in graphene in the anticorrosion using first-principles theoretical modeling. Experiments in the highly reactive environment indicate that the oxidized products primarily distribute along the grain boundaries of graphene...
March 20, 2017: ACS Applied Materials & Interfaces
Pawel Strak, Konrad Sakowski, Pawel Kempisty, Stanislaw Krukowski
A new scenario for the thermalization process of adsorbates at solid surfaces is proposed. The scenario is based on the existence of an electric dipole layer in which the electron wavefunctions extend over the positive ions, creating a strong local electric field which drags the electrons into the solid interior and repels the positive ions. During adsorption the electrons tunnel into the solid interior, conveying the excess energy. The positive ions are retarded by the field, losing the excess kinetic energy, and are located smoothly into the adsorption sites...
March 20, 2017: Physical Chemistry Chemical Physics: PCCP
Seho Yi, Jin-Ho Choi, Hyun-Jung Kim, Chul Hong Park, Jun-Hyung Cho
Chemical modification of graphene with adatoms is of importance for nanoelectronics applications. Based on first-principles density-functional theory calculations including van der Waals interactions, we present a comparative study of the diffusion characteristics of oxygen (O) and fluorine (F) atoms both on graphene and between the layers of bilayer graphene. We find that the calculated diffusion barrier for the O atom increases slightly from 0.81 eV on graphene to 0.85 eV within bilayer graphene, while that for the F atom largely decreases from 0...
March 20, 2017: Physical Chemistry Chemical Physics: PCCP
Ayaka Yamanaka, Susumu Okada
We studied the polarity of h-BN nano-flakes in terms of their edge geometries, edge hydrogen termination, and uniaxial strain by evaluating their electrostatic potential using density functional theory. Our calculations have shown that the polarity of the nanoribbons is sensitive to their edge shape, edge termination, and uniaxial tensile strain. Polarity inversion of the ribbons can be induced by controlling the hydrogen concentration at the edges and the uniaxial tensile strain. The polarity inversion indicates that h-BN nanoribbons can exhibit non-polar properties at a particular edge hydrogen concentration and tensile strain, even though the nanoribbons essentially have polarity at the edge...
March 20, 2017: Physical Chemistry Chemical Physics: PCCP
Lei Tao, Fanchen Meng, Shudong Zhao, Yongli Song, Jianxin Yu, Xianjie Wang, Zhiguo Liu, Yi Wang, Bingsheng Li, Yang Wang, Yu Sui
Bulk TMDCs are diamagnetic materials; however, two-dimensional TMDCs exhibit spin polarized edge states, which results in a coupling between the unsaturated transition metal and chalcogenide atoms at the edges. The magnetism in two-dimensional TMDCs broadens their applications in spintronic and multi-functional devices. Herein, by combining macro/micro-magnetic experimental measurements and density functional theory (DFT) calculations, we demonstrate that among five possible edge-terminated WSe2 nanosheets only two types have a magnetic ground state, corresponding to the 100% Se edge terminated and 50% Se edge terminated nanosheets, respectively...
March 20, 2017: Nanoscale
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