Read by QxMD icon Read

Quantum theory

Mercedes Vanessa Bohnwagner, Andreas Dreuw
Recently, two contradicting experimental investigations by Zachariasse et al. (J. Phys. Chem. A, 2017, 121, 1223) and Fujiwara et al. (Chem. Phys. Lett., 2013, 586, 70) have been published on the fluorescence behavior of FDMA. Motivated by the discrepancies between these studies we have examined the deactivation pathways of photoexcited FDMA using high-level quantum chemical methods like time-dependent density functional theory (TDDFT), coupled cluster (CC2) and algebraic-diagrammatic construction scheme (ADC(2), ADC(3)) simulating solvation using continuum solvation models...
July 20, 2017: Journal of Physical Chemistry. A
Ignat Harczuk, Balazs Nagy, Frank Jensen, Olav Vahtras, Hans Ågren
We present a new way to compute the two-body contribution to the dispersion energy using ab initio theory. By combining the complex polarization propagator method and the LoProp transformation, local contributions to the Casimir-Polder interaction is obtained. The full dispersion energy in dimer systems consisting of pairs of molecules including H2, N2, CO, CH4, pyridine, and benzene is investigated, where anisotropic as well as isotropic models of dispersion are obtained using a decomposition scheme for the dipole-dipole polarizability...
July 20, 2017: Physical Chemistry Chemical Physics: PCCP
Johannes Gooth, Anna C Niemann, Tobias Meng, Adolfo G Grushin, Karl Landsteiner, Bernd Gotsmann, Fabian Menges, Marcus Schmidt, Chandra Shekhar, Vicky Süß, Ruben Hühne, Bernd Rellinghaus, Claudia Felser, Binghai Yan, Kornelius Nielsch
The conservation laws, such as those of charge, energy and momentum, have a central role in physics. In some special cases, classical conservation laws are broken at the quantum level by quantum fluctuations, in which case the theory is said to have quantum anomalies. One of the most prominent examples is the chiral anomaly, which involves massless chiral fermions. These particles have their spin, or internal angular momentum, aligned either parallel or antiparallel with their linear momentum, labelled as left and right chirality, respectively...
July 19, 2017: Nature
Barry Bradlyn, L Elcoro, Jennifer Cano, M G Vergniory, Zhijun Wang, C Felser, M I Aroyo, B Andrei Bernevig
Since the discovery of topological insulators and semimetals, there has been much research into predicting and experimentally discovering distinct classes of these materials, in which the topology of electronic states leads to robust surface states and electromagnetic responses. This apparent success, however, masks a fundamental shortcoming: topological insulators represent only a few hundred of the 200,000 stoichiometric compounds in material databases. However, it is unclear whether this low number is indicative of the esoteric nature of topological insulators or of a fundamental problem with the current approaches to finding them...
July 19, 2017: Nature
Cheng Zhan, Cheng Lian, Yu Zhang, Matthew W Thompson, Yu Xie, Jianzhong Wu, Paul R C Kent, Peter T Cummings, De-En Jiang, David J Wesolowski
Supercapacitors such as electric double-layer capacitors (EDLCs) and pseudocapacitors are becoming increasingly important in the field of electrical energy storage. Theoretical study of energy storage in EDLCs focuses on solving for the electric double-layer structure in different electrode geometries and electrolyte components, which can be achieved by molecular simulations such as classical molecular dynamics (MD), classical density functional theory (classical DFT), and Monte-Carlo (MC) methods. In recent years, combining first-principles and classical simulations to investigate the carbon-based EDLCs has shed light on the importance of quantum capacitance in graphene-like 2D systems...
July 2017: Advanced Science (Weinheim, Baden-Wurttemberg, Germany)
Ellen Swann, Michael Fernandez, Michelle L Coote, Amanda S Barnard
Current benchmarking methods in quantum chemistry rely on databases that are built using a chemist's intuition. It is not fully understood how diverse or representative these databases truly are. Multivariate statistical techniques like archetypal analysis and K-means clustering have previously been used to summarise large sets of nanoparticles however molecules are more diverse and not as easily characterised by descriptors. In this work we compare three sets of descriptors based on the one-, two- and three-dimensional structure of a molecule...
July 19, 2017: ACS Combinatorial Science
Salvatore Lorenzo, Jamir Marino, Francesco Plastina, G Massimo Palma, Tony J G Apollaro
Universality is key to the theory of phase transitions, stating that the equilibrium properties of observables near a phase transition can be classified according to few critical exponents. These exponents rule an universal scaling behaviour that witnesses the irrelevance of the model's microscopic details at criticality. Here we discuss the persistence of such a scaling in a one-dimensional quantum Ising model under sinusoidal modulation in time of its transverse magnetic field. We show that scaling of various quantities (concurrence, entanglement entropy, magnetic and fidelity susceptibility) endures up to a stroboscopic time τ bd , proportional to the size of the system...
July 18, 2017: Scientific Reports
Debarati Dey, Pradipta Roy, Debashis De
The Field Effect Transistor (FET) characteristics has been observed from a single-walled Adenine nanotube device using Density Functional Theory associated with Non Equilibrium Green's Function based First Principle approach. This device is electrically doped which shows both n and p channel characteristics of a p-i-n FET. This device is designed and originated from a single-walled biomolecular nanotube structure. The p and n regions have been induced at the two ends of the device using electrical doping process...
July 10, 2017: Journal of Molecular Graphics & Modelling
Ravichandran Bhuvaneswari, Lakshmanan Sandhiya, Kittusamy Senthilkumar
The oxidation mechanism of monochloroacetic acid (CH2ClCOOH) by OH radical has been systematically investigated employing quantum mechanical methods coupled with kinetic calculation using canonical variational transition state theory. Three distinct transition states were identified for the titled reaction, two corresponding to the hydrogen atom abstraction and one corresponding to the chlorine atom abstraction. The rate constant of the titled reactions are computed over the temperature range of 278-350 K and the branching ratios calculated for the hydrogen atom abstraction from -C(O)OH site and -CH2Cl site is 25% and 75%, respectively at 298K...
July 18, 2017: Journal of Physical Chemistry. A
Barbara Chiavarino, Maria Elisa Crestoni, Simonetta Fornarini, Debora Scuderi, Jean-Yves Salpin
The complex obtained by the reaction of cisplatin and 2'-deoxyadenosine-5'-monophosphate (5'-dAMP) in water has been isolated and detected by electrospray ionization mass spectrometry. The so-formed cis-[PtCl(NH3)2(5'-dAMP)](+) complex has been studied in detail by infrared multiple photon dissociation (IRMPD) spectroscopy in two spectral ranges, namely, 700-1900 and 2800-3800 cm(-1), backed by quantum-chemical calculations at the B3LYP/LACV3P/6-311G** level of theory. In agreement with the computational results, the vibrational spectroscopic characterization of cis-[PtCl(NH3)2(5'-dAMP)](+) shows that the sampled ionic population comprises two major isomers, differentiated in the X-H stretching region by their distinct fragmentation patterns...
July 18, 2017: Inorganic Chemistry
Blazej Jaworowski, Nick Rogers, Marek Grabowski, Pawel Hawrylak
We show here how to create macroscopic quantum states in a semiconductor device: a chain of InAs quantum dots embedded in an InP nanowire. Filling the nanowire with 4 electrons per dot creates a synthetic spin-one chain, with four-fold degenerate topological ground state protected by a Haldane gap. The four states correspond to two spin-½ quasiparticles localised at the ends of the macroscopic wire. The quasiparticle spins are mapped onto a robust, macroscopic, singlet-triplet qubit. These predictions are supported by a microscopic theory and extensive numerical simulations...
July 17, 2017: Scientific Reports
Miguel A Caro, Olga Lopez-Acevedo, Tomi Laurila
We present a complete methodology to consistently estimate redox potentials strictly from first principles, without any experimental input. The methodology is based on (i) ab initio molecular dynamics (MD) simulations, (ii) all-atom explicit solvation, (iii) the two-phase thermodynamic (2PT) model and (iv) the use of electrostatic potentials as references for the absolute electrochemical scale. We apply the approach presented to compute reduction potentials of the following redox couples: Cr(+2/+3), V(+2/+3), Ru(NH3)6(+2/+3), Sn(+2/+4), Cu(+1/+2), FcMeOH(0/+1) and Fe(+2/+3) (in aqueous solution) and Fc(0/+1) (in acetonitrile)...
July 17, 2017: Journal of Chemical Theory and Computation
Ulyana G Letuta, Vitaly L Berdinskiy, Chikako Udagawa, Yoshifumi Tanimoto
Primary biological magnetoreceptors in living organisms is one of the main research problems in magnetobiology. Intracellular enzymatic reactions accompanied by electron transfer have been shown to be receptors of magnetic fields, and spin-dependent ion-radical processes can be a universal mechanism of biological magnetosensitivity. Magnetic interactions in intermediate ion-radical pairs, such as Zeeman and hyperfine (HFI) interactions, in accordance with proposed strict quantum mechanical theory, can determine magnetic-field dependencies of reactions that produce biologically important molecules needed for cell growth...
July 17, 2017: Bioelectromagnetics
Jie Pan, Stephan Lany, Yue Qi
Two-dimensional (2D) materials offer many key advantages to innovative applications, such as spintronics and quantum information processing. Theoretical computations have accelerated 2D materials design. In this issue of ACS Nano, Kumar et al. report that ferromagnetism can be achieved in functionalized nitride MXene based on first-principles calculations. Their computational results shed light on a potentially vast group of materials for the realization of 2D magnets. In this Perspective, we briefly summarize the promising properties of 2D materials and the role theory has played in predicting these properties...
July 17, 2017: ACS Nano
Robert L Z Hoye, Lana C Lee, Rachel C Kurchin, Tahmida N Huq, Kelvin H L Zhang, Melany Sponseller, Lea Nienhaus, Riley E Brandt, Joel Jean, James Alexander Polizzotti, Ahmed Kursumović, Moungi G Bawendi, Vladimir Bulović, Vladan Stevanović, Tonio Buonassisi, Judith L MacManus-Driscoll
Bismuth-based compounds have recently gained increasing attention as potentially nontoxic and defect-tolerant solar absorbers. However, many of the new materials recently investigated show limited photovoltaic performance. Herein, one such compound is explored in detail through theory and experiment: bismuth oxyiodide (BiOI). BiOI thin films are grown by chemical vapor transport and found to maintain the same tetragonal phase in ambient air for at least 197 d. The computations suggest BiOI to be tolerant to antisite and vacancy defects...
July 17, 2017: Advanced Materials
Tomasz Jakubczyk, Valentin Delmonte, Sarah Fischbach, Daniel Wigger, Doris E Reiter, Quentin Mermillod, Peter Schnauber, Arsenty Kaganskiy, Jan-Hindrik Schulze, André Strittmatter, Sven Rodt, Wolfgang Langbein, Tilmann Kuhn, Stephan Reitzenstein, Jacek Kasprzak
Optimized light-matter coupling in semiconductor nanostructures is a key to understand their optical properties and can be enabled by advanced fabrication techniques. Using in situ electron beam lithography combined with a low-temperature cathodoluminescence imaging, we deterministically fabricate microlenses above selected InAs quantum dots (QDs), achieving their efficient coupling to the external light field. This enables performing four-wave mixing microspectroscopy of single QD excitons, revealing the exciton population and coherence dynamics...
December 21, 2016: ACS Photonics
Z K Sanusi, T Govender, G E M Maguire, S B Maseko, J Lin, H G Kruger, B Honarparvar
Human immune virus subtype C is the most widely spread HIV subtype in Sub-Sahara Africa and South Africa. A profound structural insight on finding potential lead compounds is therefore necessary for drug discovery. The focus of this study is to rationalize the nine Food and Drugs Administration (FDA) HIV antiviral drugs complexed to subtype B and C-SA PR using ONIOM approach. To achieve this, an integrated two-layered ONIOM model was used to optimize the geometrics of the FDA approved HIV-1 PR inhibitors for subtype B...
June 29, 2017: Journal of Molecular Graphics & Modelling
Ekin D Cubuk, Brad D Malone, Berk Onat, Amos Waterland, Efthimios Kaxiras
Many structural and mechanical properties of crystals, glasses, and biological macromolecules can be modeled from the local interactions between atoms. These interactions ultimately derive from the quantum nature of electrons, which can be prohibitively expensive to simulate. Machine learning has the potential to revolutionize materials modeling due to its ability to efficiently approximate complex functions. For example, neural networks can be trained to reproduce results of density functional theory calculations at a much lower cost...
July 14, 2017: Journal of Chemical Physics
Mariachiara Pastore, Xavier Assfeld, Edoardo Mosconi, Antonio Monari, Thibaud Etienne
We report a theoretical study on the analysis of the relaxed one-particle difference density matrix characterizing the passage from the ground to the excited state of a molecular system, as obtained from time-dependent density functional theory. In particular, this work aims at using the physics contained in the so-called Z-vector, which differentiates between unrelaxed and relaxed difference density matrices to analyze excited states' nature. For this purpose, we introduce novel quantum-mechanical quantities, based on the detachment/attachment methodology, for analysing the Z-vector transformation for different molecules and density functional theory functionals...
July 14, 2017: Journal of Chemical Physics
Daniel R Martin, Dmitry V Matyushov
Complex I is a part of the respiration energy chain converting the redox energy into the cross-membrane proton gradient. The electron-transfer chain of iron-sulfur cofactors within the water-soluble peripheral part of the complex is responsible for the delivery of electrons to the proton pumping subunit. The protein is porous to water penetration and the hydration level of the cofactors changes when the electron is transferred along the chain. High reaction barriers and trapping of the electrons at the iron-sulfur cofactors are prevented by the combination of intense electrostatic noise produced by the protein-water interface with the high density of quantum states in the iron-sulfur clusters caused by spin interactions between paramagnetic iron atoms...
July 14, 2017: Scientific Reports
Fetch more papers »
Fetching more papers... Fetching...
Read by QxMD. Sign in or create an account to discover new knowledge that matter to you.
Remove bar
Read by QxMD icon Read

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"