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https://www.readbyqxmd.com/read/28538206/spectroscopic-far-or-terahertz-mid-infrared-and-raman-investigation-thermal-analysis-and-biological-activity-of-piplartine
#1
Anubha Srivastava, T Karthick, B D Joshi, Rashmi Mishra, Poonam Tandon, A P Ayala, Javier Ellena
Research in the field of medicinal plants including Piper species like long pepper (Piper longum L.- Piperaceae) is increasing all over the world due to its use in traditional and Ayurvedic medicine. Piplartine (piperlongumine, 5,6-dihydro-1-[(2E)-1-oxo-3-(3,4,5-trimethoxyphenyl)-2-propenyl]-2(1H)-pyridinone), a biologically active alkaloid/amide was isolated from the phytochemical investigations of Piper species, as long pepper. This alkaloid has cytotoxic, anti-fungal, anti-diabetic, anti-platelet aggregation, anti-tumoral, anxiolytic, anti-depressant, anti-leishmanial, and genotoxic activities, but, its anticancer property is the most promising and has been widely explored...
May 5, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
https://www.readbyqxmd.com/read/28537746/classical-dynamics-simulations-of-dissociation-of-protonated-tryptophan-in-the-gas-phase
#2
Yogeshwaran Krishnan, Nishant Sharma, Upakarasamy Lourderaj, Manikandan Paranjothy
Gas phase decomposition of protonated amino acids are of great interest due to their role in understanding protein and peptide chemistry. Several experimental and theoretical studies have been reported in the literature on this subject. In the present work, decomposition of the aromatic amino acid protonated tryptophan was studied by on-the-fly classical chemical dynamics simulations using density functional theory. Mass spectrometry and electronic structure theory studies have shown multiple dissociation pathways for this biologically relevant molecule...
May 24, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28537743/er-3-photoluminescence-in-er2-c82-and-er2c2-c82-metallofullerenes-elucidated-by-density-functional-theory
#3
Jian Wang, Yuan-Yuan Zhao, Po-Heng Lee, Stephan Irle
Metallofullerenes with two erbium atoms encapsulated in IPR C82 cage isomers Cs-6 (I), C2v-9 (II), and C3v-8 (III) were investigated using density functional theory. The calculations suggest that erbium atoms assume a trivalent state with Er (4f(11)) valence electronic configuration in Er2@C82 and Er2C2@C82, where two electrons (6s(2)) per Er atom are transferred to the cage carrying four negative charges (C82(4-)), while the third electron is promoted from the 4f to the 5d shell, becoming involved in covalent bonding to near atoms...
May 24, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28537733/crystal-structure-induced-preferential-surface-alloying-of-sb-on-wurtzite-zinc-blende-gaas-nanowires
#4
Martin Hjort, Peter Kratzer, Sebastian Lehmann, Sahil J Patel, Kimberly A Dick, Chris J Palmstrom, Rainer Timm, Anders Mikkelsen
We study the surface diffusion and alloying of Sb into GaAs nanowires (NWs) with controlled axial stacking of wurtzite (Wz) and zinc blende (Zb) crystal phases. Using atomically resolved scanning tunneling microscopy, we find that Sb preferentially incorporates into the surface layer of the {110}-terminated Zb segments rather than the {112 ̅0}-terminated Wz segments. Density functional theory calculations verify the higher surface incorporation rate into the Zb phase and find that it is related to differences in the energy barrier of the Sb-for-As exchange reaction on the two surfaces...
May 24, 2017: Nano Letters
https://www.readbyqxmd.com/read/28535459/spectra-structure-correlations-of-saturated-and-unsaturated-medium-chain-fatty-acids-near-infrared-and-anharmonic-dft-study-of-hexanoic-acid-and-sorbic-acid
#5
Justyna Grabska, Krzysztof B Beć, Mika Ishigaki, Marek J Wójcik, Yukihiro Ozaki
Quantum chemical reproduction of entire NIR spectra is a new trend, enabled by contemporary advances in the anharmonic approaches. At the same time, recent increase of the importance of NIR spectroscopy of biological samples raises high demand for gaining deeper understanding of NIR spectra of biomolecules, i.e. fatty acids. In this work we investigate saturated and unsaturated medium-chain fatty acids, hexanoic acid and sorbic acid, in the near-infrared region. By employing fully anharmonic density functional theory (DFT) calculations we reproduce the experimental NIR spectra of these systems, including the highly specific spectral features corresponding to the dimerization of fatty acids...
May 13, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
https://www.readbyqxmd.com/read/28534913/theoretical-investigation-of-energy-gap-bowing-in-cdsxse1-x-alloy-quantum-dots
#6
Laxman Tatikondewar, Anjali Kshirsagar
To investigate energy gap bowing in homogeneously alloyed CdSxSe1-x quantum dots (QDs) and to understand whether it is different from bulk, we perform density functional theory based electronic structure calculations for spherical QDs of different compositions x (0 ≤ x ≤ 1) and of varying sizes (2.2 to 4.6 nm). We find the bowing constant to be slightly higher than in bulk for different sizes of quantum dots. The change in the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap of QDs mainly arises due to the change in the LUMO energies...
May 23, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28534912/prediction-on-the-light-assisted-exfoliation-of-multilayered-arsenene-by-the-photo-isomerization-of-azobenzene
#7
Jun Zhao, Chunyan Liu, Wanlin Guo, Jing Ma
The exfoliation of gray arsenic into single- or few-layered arsenene is a challenge of utmost importance. We propose here that the conformational change in the photo-isomerization of azobenzene-based photochromes might be used to promote the exfoliation of multilayered arsenene. Our density functional theory calculations show that the trans-to-cis conformational change can lead to an increase of the adjacent interlayer distance of arsenene from 6.59 Å to 11.07 Å. Starting from the transition state, the azobenzene molecule can be isomerized into the more stable trans form based on further ab initio molecular dynamics simulations...
May 23, 2017: Nanoscale
https://www.readbyqxmd.com/read/28534587/light-induced-relaxation-dynamics-of-the-ferricyanide-ion-revisited-by-ultrafast-xuv-photoelectron-spectroscopy
#8
Nicholas Engel, Sergey I Bokarev, Alexandre Moguilevski, Azhr A Raheem, Ruba Al-Obaidi, Tobias Möhle, Gilbert Grell, Katrin R Siefermann, Bernd Abel, Saadullah G Aziz, Oliver Kühn, Mario Borgwardt, Igor Yu Kiyan, Emad F Aziz
Photoinduced charge transfer in transition-metal coordination complexes plays a prominent role in photosynthesis and is fundamental for light-harvesting processes in catalytic materials. However, revealing the relaxation pathways of charge separation remains a very challenging task because of the complexity of relaxation channels and ultrashort time scales. Here, we employ ultrafast XUV photoemission spectroscopy to monitor fine mechanistic details of the electron dynamics following optical ligand-to-metal charge-transfer excitation of ferricyanide in aqueous solution...
May 23, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28534567/intrinsic-ferromagnetism-and-quantum-anomalous-hall-effect-in-a-cobr2-monolayer
#9
Peng Chen, Jin-Yu Zou, Bang-Gui Liu
The electronic, magnetic, and topological properties of a CoBr2 monolayer are studied in the framework of density-functional theory (DFT) combined with tight-binding (TB) modeling in terms of the Wannier basis. Our DFT investigation and Monte Carlo simulation show that there exists intrinsic two-dimensional ferromagnetism in the CoBr2 monolayer, thanks to the large out-of-plane magnetocrystalline anisotropic energy. Our further study indicates that the spin-orbit coupling makes it become a topologically nontrivial insulator with a quantum anomalous Hall effect and topological Chern number [script C] = 4 and its edge states can be manipulated by changing the width of its nanoribbons and applying strains...
May 23, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28534413/versatile-assembly-of-metal-coordinated-calix-4-resorcinarene-cavitands-and-cages-through-ancillary-linker-tuning
#10
Wen-Yuan Pei, Guohai Xu, Jin Yang, Hui Wu, Banglin Chen, Wei Zhou, Jian-Fang Ma
We propose a design strategy for assembly of metal-coordinated calix[4]resorcinarene cavitands and cages by tuning of the ancillary linkers. Assembly of newly functionalized cavitand with angular isophthalic acid analogs affords three intriguing metal-coordinated cavitands with deep cavities, 1a-1c. Further, by mediating appropriate spacers between two isophthalic acids, two bowl-shaped cavitands are successfully joined together to produce three elegant coordination cages with tunable sizes and shapes, 2a-2c...
May 23, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28534095/qspr-modeling-of-detonation-parameters-and-sensitivity-of-some-energetic-materials-dft-vs-pm3-calculations
#11
Jianying Zhang, Gangling Chen, Xuedong Gong
The quantitative structure-property relationship (QSPR) methodology was applied to describe and seek the relationship between the structures and energetic properties (and sensitivity) for some common energy compounds. An extended series of structural and energetic descriptors was obtained with density functional theory (DFT) B3LYP and semi-empirical PM3 approaches. Results indicate that QSPR model constructed using quantum descriptors can be applied to verify the confidence of calculation results compared with experimental data...
June 2017: Journal of Molecular Modeling
https://www.readbyqxmd.com/read/28533896/sex-specific-differences-in-functional-traits-and-resource-acquisition-in-five-cycad-species
#12
Christopher Krieg, James E Watkins, Sally Chambers, Chad E Husby
Selective pressures acting on plant life histories can drive extreme specialization. One example of such specialization is the evolution of dioecious breeding systems. Evolutionary and ecological theory posits that dioecy may subject male and female individuals to different selective pressures and result in unique sex-mediated adaptive traits related to resource allocation and ecophysiology. Cycads are the earliest diverging lineage of seed plants with strict dioecy, yet we know almost nothing about the ecology and physiology of this group...
March 2017: AoB Plants
https://www.readbyqxmd.com/read/28533413/confined-catalysis-under-two-dimensional-materials
#13
Haobo Li, Jianping Xiao, Qiang Fu, Xinhe Bao
Confined microenvironments formed in heterogeneous catalysts have recently been recognized as equally important as catalytically active sites. Understanding the fundamentals of confined catalysis has become an important topic in heterogeneous catalysis. Well-defined 2D space between a catalyst surface and a 2D material overlayer provides an ideal microenvironment to explore the confined catalysis experimentally and theoretically. Using density functional theory calculations, we reveal that adsorption of atoms and molecules on a Pt(111) surface always has been weakened under monolayer graphene, which is attributed to the geometric constraint and confinement field in the 2D space between the graphene overlayer and the Pt(111) surface...
May 22, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28532662/molecular-design-of-flotation-collectors-a-recent-progress
#14
REVIEW
Guangyi Liu, Xianglin Yang, Hong Zhong
The nature of froth flotation is to selectively hydrophobize valuable minerals by collector adsorption so that the hydrophobized mineral particles can attach air bubbles. In recent years, the increasing commercial production of refractory complex ores has been urgent to develop special collectors for enhancing flotation separation efficiency of valuable minerals from these ores. Molecular design methods offer an effective way for understanding the structure-property relationship of flotation collectors and developing new ones...
May 10, 2017: Advances in Colloid and Interface Science
https://www.readbyqxmd.com/read/28532153/the-photochemical-reactivity-of-1-6-methano-10-annulene
#15
Laura Moroni, Marco Pagliai, Riccardo Chelli, Giangaetano Pietraperzia, Pier Remigio Salvi, Cristina Gellini
1,6-methano[10]annulene solutions into cyclohexane have been subjected to continuous and pulsed UV irradiation. Photolysis occurs in both cases, giving naphthalene as a minor and major product, respectively. The wavelength dependence of the reaction in solution indicates that the photochemical process occurs exciting 1,6-methano[10]annulene in the second and third singlet electronic excited states. The reaction kinetics has been determined under pulsed irradiation. From the time dependence of concentrations, along with the support of density functional theory calculations and early published data, two mechanisms are proposed for naphthalene production...
May 23, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28532025/new-tetrahedral-zinc-halide-schiff-base-complexes-synthesis-crystal-structure-theoretical-3d-hirshfeld-surface-analyses-antimicrobial-and-thermal-studies
#16
L Taghizadeh, M Montazerozohori, A Masoudiasl, S Joohari, J M White
A new bidentate Schiff base ligand named as N,N'-bis((E)-3-phenylallylidene)butane-1,4-diamine (L) and three its zinc halide complexes were synthesized and characterized by FT-IR, (1)H NMR, (13)C NMR and UV-Vis spectroscopy. The crystal structure of zinc bromide and iodide complexes were characterized using single crystal X-ray diffraction. The two structures are isomorphous, crystallizing in the monoclinic crystal system with space group C2/c with closely similar unit cell dimensions. In these complexes, the Zn(II) ion is in the center of a distorted tetrahedral environment completed by two iminic nitrogen atoms of Schiff base ligand and two halide anions...
August 1, 2017: Materials Science & Engineering. C, Materials for Biological Applications
https://www.readbyqxmd.com/read/28531817/electronic-properties-and-gas-adsorption-behaviour-of-pristine-silicon-and-boron-doped-8-0-single-walled-carbon-nanotube-a-first-principles-study
#17
Mohd Asyadi Azam, Farizul Muiz Alias, Liew Weng Tack, Raja Noor Amalina Raja Seman, Mohamad Fariz Mohamad Taib
Carbon nanotubes (CNTs) have received enormous attention due to their fascinating properties to be used in various applications including electronics, sensing, energy storage and conversion. The first principles calculations within density functional theory (DFT) have been carried out in order to investigate the structural, electronic and optical properties of un-doped and doped CNT nanostructures. O2, CO2, and CH3OH have been chosen as gas molecules to study the adsorption properties based on zigzag (8,0) SWCNTs...
May 5, 2017: Journal of Molecular Graphics & Modelling
https://www.readbyqxmd.com/read/28531764/disrupted-resting-brain-graph-measures-in-individuals-at-high-risk-for-alcoholism
#18
Bharath Holla, Rajanikant Panda, Ganesan Venkatasubramanian, Bharat Biswal, Rose Dawn Bharath, Vivek Benegal
Familial susceptibility to alcoholism is likely to be linked to the externalizing diathesis seen in high-risk offspring from high-density alcohol use disorder (AUD) families. The present study aimed at comparing resting brain functional connectivity and their association with externalizing symptoms and alcoholism familial density in 40 substance-naive high-risk (HR) male offspring from high-density AUD families and 30 matched healthy low-risk (LR) males without a family history of substance dependence using graph theory-based network analysis...
May 14, 2017: Psychiatry Research
https://www.readbyqxmd.com/read/28531346/projector-augmented-wave-method-incorporated-into-gauss-type-atomic-orbital-based-density-functional-theory
#19
Xiao-Gen Xiong, Takeshi Yanai
The Projector Augmented Wave (PAW) method developed by Blochl is well recognized as an efficient, accurate pseudopotential approach in solid-state density functional theory (DFT) calculations with plane-wave basis. Here we present an approach to incorporate the PAW method into the Gauss-type function (GTF) based DFT implementation, which is widely used for molecular quantum chemistry calculations. The nodal and high-exponent GTF components of valence molecular orbitals (MOs) are removed or pseudized by the ultrasoft PAW treatment, while there is elaborate transparency to construct accurate and well-controlled pseudopotential from all-electron atomic description and to reconstruct all-electron form of valence MOs from the pseudo MOs...
May 22, 2017: Journal of Chemical Theory and Computation
https://www.readbyqxmd.com/read/28531116/photoreactions-of-endohedral-metallofullerene-with-siliranes-electronic-properties-of-carbosilylated-lu%C3%A2-n-ih-c80
#20
Masahiro Kako, Kazuya Minami, Taiki Kuroiwa, Shinpei Fukazawa, Yuki Arikawa, Michio Yamada, Yutaka Maeda, Qiao-Zhi Li, Shigeru Nagase, Takeshi Akasaka
Photochemical carbosilylation of Lu₃N@Ih-C80 was performed using siliranes (silacyclopropanes) to afford the corresponding [5,6]- and [6,6]-adducts. Electrochemical studies indicated that the redox potentials of the carbosilylated derivatives were shifted cathodically in comparison with those of the [5,6]-pyrrolidino adducts. The electronic effect of the silirane addends on Lu₃N@Ih-C80 was verified on the basis of density functional theory calculations.
May 20, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
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