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Quantum theory

Salah Eddine Hachani, Zelikha Necira, Djamel Eddine Mazouzi, Nadia Nebbache
Quantum chemical calculations at DFT/B3LYP level of theory with 6-31G, 6-311G, and 6-311G(d,p) basis sets were done to correlate the inhibition of mild steel corrosion in 1 M H2SO4 by four dianiline Schiff bases namely N,N'-Bis(benzylidene)-4,4'-dianiline (DAA), N,N'-Bis (benzylidene)-4,4'-methylenedianiline (MDAA), N,N' Bis(benzylidene)-4,4'-sulphonyldianiline (SDAA) and N,N'-Bis(benzylidene)-4,4'-oxydianiline (ODAA) with their electronic and structural properties. Quantum chemical parameters such as the EHOMO, ELUMO, energy gap (ΔE), dipole moment (μ), global softness (σ), and global hardness (η) were calculated and discussed to provide valuable explanations for the reactivity and selectivity of the studied inhibitors...
March 2018: Acta Chimica Slovenica
Shilpa N Raja, Xingchen Ye, Matthew R Jones, Liwei Lin, Sanjay Govindjee, Robert O Ritchie
Nanoscale stress sensing is of crucial importance to biomechanics and other fields. An ideal stress sensor would have a large dynamic range to function in a variety of materials spanning orders of magnitude of local stresses. Here we show that tetrapod quantum dots (tQDs) exhibit excellent sensing versatility with stress-correlated signatures in a multitude of polymers. We further show that tQDs exhibit pressure coefficients, which increase with decreasing polymer stiffness, and vary >3 orders of magnitude...
March 20, 2018: Nature Communications
William W Parson
Rate constants for photochemical charge separation and recombination in a zinc-porphyrin-benzoquinone cyclophane are calculated by an approach that was developed recently to include effects of vibrational dephasing and relaxation and to reduce the dependence on freely adjustable parameters. The theory is extended to treat the rate of vibrational relaxation individually for each vibrational sublevel of the initial charge-transfer product. Quantum-mechanical/molecular-mechanical simulations of the reactions in iso-octane, toluene, dichloromethane and acetonitrile suggest that charge separation occurs at conical intersections in the two more polar solvents, but at avoided crossings in the nonpolar solvents...
March 20, 2018: Journal of Physical Chemistry. B
Thomas J Penfold, Etienne Gindensperger, Chantal Daniel, Christel M Marian
Intersystem crossing (ISC), formally forbidden within nonrelativistic quantum theory, is the mechanism by which a molecule changes its spin state. It plays an important role in the excited state decay dynamics of many molecular systems and not just those containing heavy elements. In the simplest case, ISC is driven by direct spin-orbit coupling between two states of different multiplicities. This coupling is usually assumed to remain unchanged by vibrational motion. It is also often presumed that spin-allowed radiationless transitions, i...
March 20, 2018: Chemical Reviews
Emmanuel Igumbor, Okikiola Olaniyan, Edwin Mapasha, Helga Danga, Ezekiel Omotoso, Walter Meyer
Electrically active induced energy levels in semiconductor devices could be beneficial to the discovery of an enhanced p or n-type semiconductor. N implanted into 4H-SiC is a high energy process that produced high defect concentrations which could be removed during dopant activation annealing. On the other hand, B substituted for silicon in SiC causes a reduction in the number of defects. This scenario leads to a decrease in the dielectric properties and induced deep donor and shallow acceptor levels. Complexes formed by N, such as the N-vacancy centre, have been reported to play a significant role in the application of quantum bits...
March 20, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Min Zhou, Qunhong Weng, Zakhar I Popov, Yijun Yang, Liubov Yu Antipina, Pavel B Sorokin, Xi Wang, Yoshio Bando, Dmitri Golberg
Electrocatalytic hydrogen evolution reaction (HER) in alkaline solution is hindered by its sluggish kinetics toward water dissociation. Nickel-based catalysts, as low-cost and effective candidates, show great potentials to replace platinum (Pt)-based materials in the alkaline media. The main challenge regarding this type of catalysts is their relatively poor durability. In this work, we conceive and construct a charge-polarized carbon layer derived from carbon quantum dots (CQDs) on Ni3 N nanostructure (Ni3 N@CQDs) surfaces, which simultaneously exhibit durable and enhanced catalytic activity...
March 20, 2018: ACS Nano
Koichiro Takao, Satoru Tsushima
The carbonate ion is an effective quencher of uranyl(vi) luminescence and makes uranyl(vi) tricarbonate barely luminescent and photochemically inactive. We demonstrate here that photoexcited uranyl(vi) tricarbonate, *[UVIO2(CO3)3]4-, can however oxidize borohydrides (BH3X-, X = H, CN) to give boric acid and H2 gas, reducing itself to [UVO2(CO3)3]5-. This hypothesis was supported by UV-vis and NMR spectroscopy as well as quantum chemical calculations. The charge transfer states associated with photoreduction processes were modelled by density functional theory calculations...
March 20, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
Wei Li, Shengmei Zhao
Bell inequality testing, a well-established method to demonstrate quantum non-locality between remote two-partite entangled systems, is playing an important role in the field of quantum information. The extension to high-dimensional entangled systems, using the so-called Bell-CGLMP inequality, points the way in measuring joint probabilities, the kernel block to construct high dimensional Bell inequalities. Here we show that in theory the joint probability of a two-partite system entangled in a Hilbert space can be measured by choosing a set of basis vectors in its dual space that are related by a Fourier transformation...
March 19, 2018: Scientific Reports
S Majid
We consider Hilbert's problem of the axioms of physics at a qualitative or conceptual level. This is more pressing than ever as we seek to understand how both general relativity and quantum theory could emerge from some deeper theory of quantum gravity, and in this regard I have previously proposed a principle of self-duality or quantum Born reciprocity as a key structure. Here, I outline some of my recent work around the idea of quantum space-time as motivated by this non-standard philosophy, including a new toy model of gravity on a space-time consisting of four points forming a square...
April 28, 2018: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
Miguel Ángel Lozada Aguilar, Andrei Khrennikov, Klaudia Oleschko
As was recently shown by the authors, quantum probability theory can be used for the modelling of the process of decision-making (e.g. probabilistic risk analysis) for macroscopic geophysical structures such as hydrocarbon reservoirs. This approach can be considered as a geophysical realization of Hilbert's programme on axiomatization of statistical models in physics (the famous sixth Hilbert problem). In this conceptual paper , we continue development of this approach to decision-making under uncertainty which is generated by complexity, variability, heterogeneity, anisotropy, as well as the restrictions to accessibility of subsurface structures...
April 28, 2018: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
Giacomo Mauro D'Ariano
I argue for a full mathematization of the physical theory, including its axioms, which must contain no physical primitives. In provocative words: 'physics from no physics'. Although this may seem an oxymoron, it is the royal road to keep complete logical coherence, hence falsifiability of the theory. For such a purely mathematical theory the physical connotation must pertain only the interpretation of the mathematics, ranging from the axioms to the final theorems. On the contrary, the postulates of the two current major physical theories either do not have physical interpretation (as for von Neumann's axioms for quantum theory), or contain physical primitives as 'clock', 'rigid rod', 'force', 'inertial mass' (as for special relativity and mechanics)...
April 28, 2018: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
Kenia Melchor-Rodríguez, Juan José Gamboa-Carballo, Anthuan Ferino-Pérez, Nady Passé-Coutrin, Sarra Gaspard, Ulises Javier Jáuregui-Haza
A theoretical study of the influence of acidic surface groups (SG) of activated carbon (AC) on chlordecone hydrate (CLDh) adsorption is presented, in order to help understanding the adsorption process under basic pH conditions. A seven rings aromatic system (coronene) with a functional group in the edge was used as a simplified model of AC to evaluate the influence of SG in the course of adsorption from aqueous solution at basic pH conditions. Two SG were modeled in their deprotonated form: carboxyl and hydroxyl (COO- and O- ), interacting with CLDh...
March 9, 2018: Journal of Molecular Graphics & Modelling
Shalini Awasthi, Shalini Gupta, Ravi Tripathi, Nisanth N Nair
Enhanced sampling of large number of collective variables (CVs) is inevitable in molecular dynamics (MD) simulations of complex chemical processes such as enzymatic reactions. Due to the computational overhead of hybrid quantum mechanical/molecular mechanical (QM/MM) based (MD) simulations, especially together with density functional theory (DFT), predictions of reaction mechanism and estimation of free energy barriers have to be carried out within few tens of picoseconds. We show here that the recently developed Temperature Accelerated Sliced Sampling (TASS) method allows one to sample large number of CVs, thereby enabling us to obtain rapid convergence in free energy estimates in QM/MM MD simulation of enzymatic reactions...
March 19, 2018: Journal of Physical Chemistry. B
Yang Yang, Tanner Culpitt, Sharon Hammes-Schiffer
The quantum mechanical treatment of both electrons and protons in the calculation of excited state properties is critical for describing nonadiabatic processes such as photoinduced proton-coupled electron transfer. Multicomponent density functional theory enables the consistent quantum mechanical treatment of more than one type of particle and has been implemented previously for studying ground state molecular properties within the nuclear-electronic orbital (NEO) framework, where all electrons and specified protons are treated quantum mechanically...
March 19, 2018: Journal of Physical Chemistry Letters
Wei-Wei Yang, Lei Li, Jing-Sheng Zhao, Xiao-Xiong Liu, Jian-Bo Deng, Xianru Hu
By doing calculations based on density functional theory (DFT), we predict that the two-dimensional anti-ferromagnetic (AFM) NiOsCl$_6$ as a Chern insulator can realize the quantum anomalous Hall (QAH) effect. We investigate the magnetocrystalline anisotropy (MAC) energies in different magnetic configurations and the N\'{e}el AFM configuration is proved to be ground state. When considering spin-orbit coupling (SOC), this layered material with spins perpendicular to the plane shows properties as a Chern insulator characterized by an inversion band structure and a nonzero Chern number...
March 19, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Anand Mohan Verma, Harshal D Kawale, Kushagra Agrawal, Nanda Kishore
In the pyrolysis of Sphagnum moss species, p-isopropenylphenol (p-IPP) is a major product which has been considered in this density functional theory based computational study for its conversion to various products such as benzene, phenol, 4-propenylphenol, indan-5-ol, 4-propylcyclohexanone, 4-cyclopropylphenol, etc. In order to achieve these products, eight different reaction schemes are performed using B3LYP/6-311 + g (d,p) level of theory. Further, thermodynamic properties such as reaction free energies and reaction enthalpies associated with these eight reaction schemes are developed in the temperature range of 298-898 K...
March 9, 2018: Journal of Molecular Graphics & Modelling
Xia Sheng, Xiaotong Jiang, Hailiang Zhao, Dongjin Wan, Yongde Liu, Cleopatra Ashley Ngwenya, Lin Du
The 1:1 complexes of two unsaturated esters with 2,2,2-trifluoroethanol (TFE) were investigated experimentally and computationally. The experimental observations of the spectral shifts of the OH-stretching vibrational transitions were obtained at 113cm-1 for TFE-methyl acrylate (MA) and 92cm-1 for TFE-vinyl acetate (VA). There are three docking sites in the two unsaturated esters for the incoming TFE. The predicted red shifts of the OH-stretching vibrational transitions were found to be larger for the OH⋯OC hydrogen bonded conformer than those for the OH⋯π and OH⋯O ones...
March 10, 2018: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Christine Khripkov, Amichay Vardi, Doron Cohen
We introduce a semiclassical theory for strong localization that may arise in the context of many-body thermalization. As a minimal model for thermalization we consider a few-site Bose-Hubbard model consisting of two weakly interacting subsystems that can exchange particles. The occupation of a subsystem (x) satisfies in the classical treatment a Fokker-Planck equation with a diffusion coefficient D(x). We demonstrate that it is possible to deduce from the classical description a quantum breaktime t^{*} and, hence, the manifestations of a strong localization effect...
February 2018: Physical Review. E
C F Clauser, N R Arista
We present a study of the stopping power of plasmas using two main approaches: the collisional (scattering theory) and the dielectric formalisms. In the former case, we use a semiclassical method based on quantum scattering theory. In the latter case, we use the full description given by the extension of the Lindhard dielectric function for plasmas of all degeneracies. We compare these two theories and show that the dielectric formalism has limitations when it is used for slow heavy ions or atoms in dense plasmas...
February 2018: Physical Review. E
T R Hartke, Y-Y Liu, M J Gullans, J R Petta
Quantum confinement leads to the formation of discrete electronic states in quantum dots. Here we probe electron-phonon interactions in a suspended InAs nanowire double quantum dot (DQD) that is electric-dipole coupled to a microwave cavity. We apply a finite bias across the wire to drive a steady state population in the DQD excited state, enabling a direct measurement of the electron-phonon coupling strength at the DQD transition energy. The amplitude and phase response of the cavity field exhibit oscillations that are periodic in the DQD energy level detuning due to the phonon modes of the nanowire...
March 2, 2018: Physical Review Letters
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