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Quantum theory

Huijuan Yuan, Songyan Feng, Keke Wen, Qiuling Zhu, Beibei An, Xugeng Guo, Jinglai Zhang
Enol-keto proton tautomerization and cis-trans isomerization reactions of a novel excited-state intramolecular proton transfer (ESIPT) fluorophore of BTImP and its protonated form (BTImP(+)) were explored using density functional theory/time-dependent density functional theory (DFT/TD-DFT) computational methods with a B3LYP hybrid functional and the 6-31+G(d,p) basis set. In addition, the absorption and fluorescence spectra were calculated at the TD-B3LYP/6-31+G(d,p) level of theory. Our results reveal that both BTImP and BTImP(+) can undergo an ultrafast ESIPT reaction, giving rise to the single fluorescence emission with different fluorescence colors, which are nicely consistent with the experimental findings...
April 19, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Mattia Sist, Carlo Gatti, Peter Nørby, Simone Cenedese, Hidetaka Kasai, Kenichi Kato, Bo B Iversen
The discovery of the ultra-high thermoelectric figure of merit of 2.6 in SnSe has drawn attention to other lead-free IV-VI orthorhombic semiconductors. GeSe has been predicted to possess thermoelectric performances comparable to SnSe. Here, a complete structural study is reported of GeSe with temperature by means of high-resolution synchrotron powder X-ray diffraction. In the orthorhombic phase, the evolution of the bond distances with temperature is shown to deviate significantly with respect to SnSe. Analysis of the chemical bonding within the Quantum Theory of Atoms in Molecules shows that GeSe is ionic with van der Waals interlayer interactions...
April 25, 2017: Chemistry: a European Journal
Yoichi Kobayashi, Hajime Okajima, Hikaru Sotome, Takeshi Yanai, Katsuya Mutoh, Yusuke Yoneda, Yasuteru Shigeta, Akira Sakamoto, Hiroshi Miyasaka, Jiro Abe
Delocalized biradicals have been extensively studied because of fundamental interests to singlet biradicals and several potential applications such as to two-photon absorption materials. However, many of the biradical studies only focus on the static properties of the rigid molecular structures. It is expected that the biradical properties of the delocalized biradicals are sensitive to the subtle changes of the molecular structures and their local environments. Therefore, the studies of the dynamic properties of the system will give further insight into stable radical chemistry...
April 25, 2017: Journal of the American Chemical Society
Rebecca A Coates, Peter B Armentrout
The experimental bond energies of Ni2+(H2O)x complexes, where x = 4 - 11, are determined by threshold collision-induced dissociation using a guided ion beam tandem mass spectrometer with an electrospray ionization source. The electrospray ionization source produces a distribution of Ni2+(H2O)x complexes, where an in-source fragmentation technique is employed to access the x = 4 - 6 complexes and control the population of excited isomers. The kinetic energy dependent cross sections are modeled to yield 0 K bond energies for sequential loss of neutral water molecules, which are converted to 298 K binding energies...
April 25, 2017: Journal of Physical Chemistry. A
Francis G Woodhouse, Jörn Dunkel
Chemically or optically powered active matter plays an increasingly important role in materials design, but its computational potential has yet to be explored systematically. The competition between energy consumption and dissipation imposes stringent physical constraints on the information transport in active flow networks, facilitating global optimization strategies that are not well understood. Here, we combine insights from recent microbial experiments with concepts from lattice-field theory and non-equilibrium statistical mechanics to introduce a generic theoretical framework for active matter logic...
April 25, 2017: Nature Communications
Xin-Hao Li, Jeffrey B Chou, Wei Lek Kwan, Asma M Elsharif, Sang-Gook Kim
We recently reported that an Au/TiO<sub>2</sub> photonic crystal device for photochemical energy conversion showed a sub-bandgap photoresponse centered at the surface plasmon polariton (SPP) resonant wavelength of this device. Here we developed a theoretical modeling of the internal photoemission in this device by incorporating the effects of anisotropic hot electron momentum distribution caused by SPP. The influences of interband and intraband transition, anisotropic momentum distribution of hot electrons by SPP are integrated to model the internal quantum efficiency (IQE) of this device...
April 17, 2017: Optics Express
Ctirad Červinka, Michal Fulem
A computational methodology for calculation of sublimation enthalpies of molecular crystals from first principles is developed and validated by comparison to critically evaluated literature experimental data. Temperature dependent sublimation enthalpies for a set of selected 22 molecular crystals in their low-temperature phases are calculated. The computational methodology consists in several building blocks based on high level electronic structure methods of quantum chemistry and statistical thermodynamics...
April 24, 2017: Journal of Chemical Theory and Computation
Claudia Kleinlein, Shao-Liang Zheng, Theodore A Betley
Three ferric dipyrromethene complexes featuring different ancillary ligands were synthesized by one electron oxidation of ferrous precursors. Four-coordinate iron complexes of the type ((Ar)L)FeX2 [(Ar)L = 1,9-(2,4,6-Ph3C6H2)2-5-mesityldipyrromethene] with X = Cl or (t)BuO were prepared and found to be high-spin (S = (5)/2), as determined by superconducting quantum interference device magnetometry, electron paramagnetic resonance, and (57)Fe Mössbauer spectroscopy. The ancillary ligand substitution was found to affect both ground state and excited properties of the ferric complexes examined...
April 24, 2017: Inorganic Chemistry
Bess Vlaisavljevich, Johanna M Huck, Zeric Hulvey, Kyuho Lee, Jarad A Mason, Jeffrey B Neaton, Jeffrey R Long, Craig M Brown, Dario Alfè, Angelos Michaelides, Berend Smit
Small molecule binding in metal-organic frameworks (MOFs) can be accurately studied both experimentally and computationally, provided the proper tools are employed. Herein, we compare and contrast properties associated with guest binding by means of density functional theory (DFT) calculations using nine different functionals for the M2(dobdc) (dobdc4- = 2,5-dioxido,1,4-benzenedicarboxylate) series where M = Mg, Mn, Fe, Co, Ni, Cu, and Zn. Additionally, we perform Quantum Monte Carlo (QMC) calculations for one system to determine if this method can be used to assess the performance of DFT...
April 24, 2017: Journal of Physical Chemistry. A
Vincent Pohl, Gunter Hermann, Jean Christophe Tremblay
The aim of the present contribution is to provide a framework for analyzing and visualizing the correlated many-electron dynamics of molecular systems, where an explicitly time-dependent electronic wave packet is represented as a linear combination of N-electron wave functions. The central quantity of interest is the electronic flux density, which contains all information about the transient electronic density, the associated phase, and their temporal evolution. It is computed from the associated one-electron operator by reducing the multideterminantal, many-electron wave packet using the Slater-Condon rules...
April 24, 2017: Journal of Computational Chemistry
Rahul D Telore, Amol G Jadhav, Nagaiyan Sekar
Synthesis of novel 3,6-di(substituted quinoxalin) carbazole fluorophores by the condensation of 1,1'-(9-ethyl-9H-carbazole-3,6-diyl)bis(2-bromoethanone) with methyl, chloro and unsubstituted o-phenylenediamine is presented. Synthesized derivatives are well characterized by (1)H NMR, (13)C NMR, FTIR and Mass spectroscopy. Photophysical studies are carried out using solvents of varying polarities revealed positive solvatochromism and intramolecular charge transfer from carbazole (Donor) to quinoxalin (Acceptor)...
April 22, 2017: Journal of Fluorescence
Elad Harel
The correlations between different quantum-mechanical degrees of freedom of molecular species dictate their chemical and physical properties. Generally, these correlations are reflected in the optical response of the system but in low-order or low-dimensionality measurement the signals are highly averaged. Here, we describe a novel four-dimensional coherent spectroscopic method that directly correlates within and between the manifold of electronic and vibrational states. The optical response theory is developed in terms of both resonant and non-resonant field-matter interactions...
April 21, 2017: Journal of Chemical Physics
Masumeh Gharabaghi, Shant Shahbazian
The quantum theory of atoms in molecules (QTAIM) is based on the clamped nucleus paradigm and solely working with the electronic wavefunctions, so does not include nuclear vibrations in the AIM analysis. On the other hand, the recently extended version of the QTAIM, called the multi-component QTAIM (MC-QTAIM), incorporates both electrons and quantum nuclei, i.e., those nuclei treated as quantum waves instead of clamped point charges, into the AIM analysis using non-adiabatic wavefunctions. Thus, the MC-QTAIM is the natural framework to incorporate the role of nuclear vibrations into the AIM analysis...
April 21, 2017: Journal of Chemical Physics
Agnieszka Roztoczyńska, Paweł Lipkowski, Justyna Kozłowska, Wojciech Bartkowiak
Nowadays, much attention is put toward the description of noncovalent complexes exposed to the high pressure or embedded in confining environments. Such conditions may strongly modify the physical and chemical properties of molecular systems. This study focuses on the theoretical description of the confinement induced changes in geometry and energetic parameters of the halogen bonded FCl⋯CNF complex. A model analytical potential is applied to render the effect of orbital compression. In order to analyze the nature of halogen bond interaction, in the presence of spatial confinement, the supermolecular approach together with the symmetry-adapted perturbation theory is used...
April 21, 2017: Journal of Chemical Physics
John S Lomas, Laurent Joubert
The idea that hydrogen bond cooperativity is responsible for the structure and reactivity of carbohydrates is examined. Density functional theory and gauge-including atomic orbital calculations on the known conformers of the α and β anomers of D-glucopyranose in the gas phase are used to compute proton NMR chemical shifts and interatomic distances, which are taken as criteria for probing intramolecular interactions. Atom-atom interaction energies are calculated by the interacting quantum atoms approach in the framework of the quantum theory of atoms in molecules...
April 22, 2017: Magnetic Resonance in Chemistry: MRC
Gehad G Mohamed, Maher M Hamed, Nadia G Zaki, Mohamed M Abdou, Marwa El-Badry Mohamed, Abanoub Mosaad Abdallah
A simple, accurate and fast spectrophotometric method for the quantitative determination of melatonin (ML) drug in its pure and pharmaceutical forms was developed based on the formation of its charge transfer complex with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as an electron acceptor. The different conditions for this method were optimized accurately. The Lambert-Beer's law was found to be valid over the concentration range of 4-100μgmL(-1) ML. The solid form of the CT complex was structurally characterized by means of different spectral methods...
April 4, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Qianglu Lin, Hyeong Jin Yun, Wenyong Liu, Hyung-Jun Song, Nikolay S Makarov, Oleksandr Isaienko, Tom Nakotte, Gen Chen, Hongmei Luo, Victor I Klimov, Jeffrey M Pietryga
The use of semiconductor nanocrystal quantum dots (QDs) in optoelectronic devices typically requires post-synthetic chemical surface treatments to enhance electronic coupling between QDs and allow for efficient charge transport in QD films. Despite their importance to solar cells, and infrared (IR) light-emitting diodes and photodetectors, advances in these chemical treatments for lead chalcogenide (PbE, E = S, Se, Te) QDs have lagged behind those of, for instance, II-VI semiconductor QDs. Here, we introduce a method for fast and effective ligand exchange for PbE QDs in solution, resulting in QDs completely passivated by a wide range of small anionic ligands...
April 21, 2017: Journal of the American Chemical Society
M Lohöfer, S Wessel
By means of large-scale quantum Monte Carlo simulations, we examine the quantum critical scaling of the magnetic excitation gap (the triplon gap) in a three-dimensional dimerized quantum antiferromagnet, the bicubic lattice, and identify characteristic multiplicative logarithmic scaling corrections atop the leading mean-field behavior. These findings are in accord with field-theoretical predictions that are based on an effective description of the quantum critical system in terms of an asymptotically free field theory, which exhibits a logarithmic decay of the renormalized interaction strength upon approaching the quantum critical point...
April 7, 2017: Physical Review Letters
Sandro Stringari
By developing the hydrodynamic theory of spinor superfluids, we calculate the moment of inertia of a harmonically trapped Bose-Einstein condensate with spin-orbit coupling. We show that the velocity field associated with the rotation of the fluid exhibits diffused vorticity, in contrast to the irrotational behavior characterizing a superfluid. Both Raman-induced and Rashba spin-orbit couplings are considered. In the first case the moment of inertia takes the rigid value at the transition between the plane wave and the single minimum phase, while in the latter case the rigid value is achieved in the limit of isotropic Rashba coupling...
April 7, 2017: Physical Review Letters
Uwe Manthe
Multi-configurational time-dependent Hartree (MCTDH) based approaches are efficient, accurate, and versatile methods for high-dimensional quantum dynamics simulations. Applications range from detailed investigations of polyatomic reaction processes in the gas phase to high-dimensional simulations studying the dynamics of condensed phase systems described by typical solid state physics model Hamiltonians. The present article presents an overview of the different areas of application and provides on a comprehensive review of the underlying theory...
April 21, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
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