Filters
total: 1989
filtered: 1737
-
Catalog
Chosen catalog filters
displaying 1000 best results Help
Search results for: QUANTUM SCATTERING CALCULATIONS
-
Toward Mechanosynthesis of diamondoid structures: III. Quantum-chemical study of silylene molecule and silicon atom transfer mechanism from caped SWCNT tip to the reaction center on a hydrogenated Si(111) surface
PublicationOpublikowana wcześniej (Modelling Simul. Mater. Sci. Eng., Vol. 7, 1999, pp. 43-58) strategia mechanosyntezy struktur krzemu na uwodornionej płaszczyźnie Si(111) została poszerzona poprzez uwzględnienie ostrza w postaci zamkniętej SWCNT jako urządzenia kontrolującego położenie cząsteczki sililenu oraz atomu krzemu.
-
Intramolecular transformation of an antifungal antibiotic nystatin A1 into its isomer, iso-nystatin A1 - structural and molecular modeling studies
PublicationNystatin A1, a polyene macrolide antifungal antibiotic, in a slightly basic or acidic solution undergoes an intramolecular transformation, yielding a structural isomer, the translactonization product, iso-nystatin A1 with lactone ring diminished by two carbon atoms. Structural evidence is provided by advanced NMR and Mass Spectrometry (MS) studies. Molecular dynamics simulations and quantum mechanics calculations gave the insight...
-
NbIr 2 B 2 and TaIr 2 B 2 – New Low Symmetry Noncentrosymmetric Superconductors with Strong Spin–Orbit Coupling
PublicationSuperconductivity was first observed more than a century ago, but the search for new superconducting materials remains a challenge. The Cooper pairs in superconductors are ideal embodiments of quantum entanglement. Thus, novel superconductors can be critical for both learning about electronic systems in condensed matter and for possible application in future quantum technologies. Here two previously unreported materials, NbIr2B2...
-
Potential energy surfaces of the low-lying electronic states of the Li+LiCs system
PublicationAb initio quantum chemistry calculations are performed for the mixed alkali triatomic system. Global minima of the ground and first excited doublet states of the trimer are found and Born-Oppenheimer potential energy surfaces of the Li atom interacting with the LiCs molecule were calculated for these states. The lithium atom is placed at various distances and bond angles from the lithium-caesium dimer. Three-body nonadditive forces...
-
Jahn-Teller and related conical intersections in the benzene radical cation and the monofluoro derivate
PublicationThe multi-state multi-mode vibronic interactions in the benzene radical cation and its monofluoro derivative have been investigated theoretically, based on high-level electronic structure calculations for the system parameters and a quantum treatment of the nuclear motion. The available experimental data are well reproduced. The interplay of different vibronic coupling mechanisms is pointed out leading to multiple nonadiabatic...
-
Stark effect of atomic helium singlet lines
PublicationWe present experimental and theoretical investigations of the He spectral series 2S1−nQ1 (n=3÷9, Q=S,P,D,…,n−1) and 2P1−nQ1 (n=3÷9, Q=S,P,D,…,n−1) in electric fields up to 1635 kV/cm. Apart from the allowed transitions with |ΔL|=1, the transitions with |ΔL|=0,2,3,…-without field strictly forbidden-were observed. Several He patterns become similar to hydrogen patterns, which means they are nearly symmetric and show in higher fields...
-
Calculating the Partition Coefficients of Organic Solvents in Octanol/Water and Octanol/Air
PublicationPartition coefficients define how a solute is distributed between two immiscible phases at equilibrium. The experimental estimation of partition coefficients in a complex system can be an expensive, difficult, and time-consuming process. Here a computational strategy to predict the distributions of a set of solutes in two relevant phase equilibria is presented. The octanol/water and octanol/air partition coefficients are predicted...
-
The influence of anchoring group position in ruthenium dye molecule on performance of dye-sensitized solar cells
PublicationThe effect of anchoring group position and, in consequence, the orientation of the ruthenium dye molecule on titania surface on the performance of dye-sensitized solar cells has been studied intensively. Three model ruthenium sensitizing dyes bearing carboxylic anchoring group in ortho, meta or para position were synthesized and well characterized by spectroscopic, electrochemical, photophysical and photochemical measurements....
-
TINKTEP: A fully self-consistent, mutually polarizable QM/MM approach based on the AMOEBA force field
PublicationWe present a novel quantum mechanical/molecular mechanics (QM/MM) approach in which a quantum subsystem is coupled to a classical subsystem described by the AMOEBA polarizable force field. Our approach permits mutual polarization between the QM and MM subsystems, effected through multipolar electrostatics. Self-consistency is achieved for both the QM and MM subsystems through a total energy minimization scheme. We provide an expression...
-
Production of singlet oxygen atoms by photodissociation of oxywater
PublicationQuantum chemical calculations are reported for the energies of the few lowest electronic singlet states of oxywater along dissociation of the oxygen-oxygen bond into water and singlet oxygen using multistate multireference second-order Møller–Plesset perturbation theory. We compute an energy of 21 kcal/mol to remove one oxygen atom in the lowest singlet state. The two lowest excited singlet states have vertical excitation energies...
-
Impact of dyes isomerization effect on the charge transfer phenomenon occurring on the dye/nanosemiconductor interface
PublicationThe present work aimed to find the answer how does the isomerization of the Ru based dyes affect the overall photon-to-current efficiency of the DSSCs and to explain the charge transfer phenomenon occurring on the dye/ nanosemiconductor interface. Therefore, electronic and optical properties of three bipyridine derivatives anchored on the TiO2 electrode were investigated by computational simulations based on quantum chemistry codes...
-
The ONETEP linear-scaling density functional theory program
PublicationWe present an overview of the ONETEP program for linear-scaling density functional theory (DFT) calculations with large basis set (planewave) accuracy on parallel computers. The DFT energy is computed from the density matrix, which is constructed from spatially localized orbitals we call Non-orthogonal Generalized Wannier Functions (NGWFs), expressed in terms of periodic sinc (psinc) functions. During the calculation, both the...
-
Hydrogen migration in formation of NH(A3Π) radicals via superexcited states in photodissociation of isoxazole molecules
PublicationFormation of the excited NH(A 3Π) free radicals in the photodissociation of isoxazole (C3H3NO) molecules has been studied over the 14-22 eV energy range using photon-induced fluorescence spectroscopy. The NH(A 3Π) is produced through excitation of the isoxazole molecules into higher-lying superexcited states. Observation of the NH radical, which is not a structural unit of the isoxazole molecule, corroborates the hydrogen atom...
-
Wpływ parametrów strugi paliwa wtryskiwanego do cylindra silnika okrętowego na początkową fazę rozpylania
PublicationPrzedmiotem rozprawy jest analiza procesu wtrysku oleju napędowego do cylindra silnika okrętowego z zapłonem samoczynnym i bezpośrednim wtryskiem paliwa. Analiza tego zagadnienia została przeprowadzona w aspekcie wpływu makro parametrów strugi na początkową fazę rozpylania oleju napędowego. Celem niniejszej pracy jest określenie wpływu współczynnika L/D (długość otworu/średnica) otworu wylotowego wtryskiwacza na zmianę charakterystyki...
-
Unraveling the role of boron dimers in the electrical anisotropy and superconductivity in boron-doped diamond
PublicationWe use quantum mechanics (QM) to determine the states formed by B dopants in diamond. We find that isolated B sites prefer to form BB dimers and that the dimers pair up to form tetramers (BBCBB) that prefer to aggregate parallel to the (111) surface in the <110> direction, one double layer below the H-terminated surface double layer. These tetramers lead to metallic character (Mott metal Insulator Transition) with holes in the...
-
Theoretical and Experimental Studies on the Visible Light Activity of TiO2 Modified with Halide-Based Ionic Liquids
PublicationFormation of a surface complex between organic molecules and TiO2 is one of the possible strategies for the development of visible light-induced TiO2 photoactivity. Herein, three ionic liquids (ILs) with the same cation and dierent anions (1-butylpirydynium chloride/bromide/iodide) have been applied for the surface modification of TiO2 and to understand the role of anions in visible light-induced activity of ILs-TiO2 systems. Photocatalytic...
-
Elimination and migration of hydrogen in the vacuum-ultraviolet photodissociation of pyridine molecules
PublicationElimination of the excited hydrogen atoms H(n), n = 4–7, and hydrogen migration in formation of the excited NH(A 3Π) free radicals in the photodissociation of pyridine, C5H5N, molecules have been studied over the 17.5–70 eV photon energy range. In the measurements the photon-induced fluorescence spectroscopy technique has been applied. Both fragments are produced through excitation of pyridine molecules into higher-lying superexcited...
-
Kagome Lattice Promotes Chiral Spin Fluctuations
PublicationDynamical spin fluctuations in magnets can be endowed with a slight bent toward left- or right-handed chirality by Dzyaloshinskii-Moriya interactions. However, little is known about the crucial role of lattice geometry on these chiral spin fluctuations and on fluctuation-related transport anomalies driven by the quantum-mechanical (Berry) phase of conduction electrons. Via thermoelectric Nernst effect and electric Hall effect experiments,...
-
Electrochemical, theoretical and surface physicochemical studies of the alkaline copper corrosion inhibition by newly synthesized molecular complexes of benzenediamine and tetraamine with π acceptor
PublicationTwo charge transfer complexes, namely [(BDAH)+(PA−)] CT1 [(BTAH)2+(PA−)2] and CT2 (BDAH = 1,2-benzenediamine, BTAH = 1,2,4,5-benzenetetramine, and PA− = 2,4,6-trinitrophenolate), were synthesized and fully characterized using various spectroscopic techniques. CT1 and CT2 were tested as inhibitors to effectively control the uniform and anodic corrosion processes of copper in an alkaline electrolyte (1.0 M KOH) using various electrochemical...
-
Novel approach to modeling spectral-domain optical coherence tomography with Monte Carlo method
PublicationNumerical modeling Optical Coherence Tomography (OCT) systems is needed for optical setup optimization, development of new signal processing methods and assessment of impact of different physical phenomena inside the sample on OCT signal. The Monte Carlo method has been often used for modeling Optical Coherence Tomography, as it is a well established tool for simulating light propagation in scattering media. However, in this method...
-
Evolution of Ag nanostructures created from thin films: UV–vis absorption and its theoretical predictions
PublicationAg-based plasmonic nanostructures were manufactured by thermal annealing of thin metallic films. Structure and morphology were studied using scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM) and X-ray photoelectron spectroscopy (XPS). SEM images show that the formation of nanostructures is influenced by the initial layer thickness as well as the...
-
Experimentally feasible semi-device-independent certification of four-outcome positive-operator-valued measurements
PublicationRecently the quantum information science community devoted a lot of attention to the theoretical and practical aspects of generalized measurements, the formalism of all possible quantum operations leading to acquisition of classical information. On the other hand, due to imperfections present in quantum devices, and limited thrust to them, a trend of formulating quantum information tasks in a semi-device-independent manner emerged....
-
A non-adiabatic wavepacket dynamical study of the low energy chargetransfer process in the S3+ + H collision
PublicationThe collisional system S3+ + H?S2+ + H+ has been studied using a time-dependent wavepacket methodologyin two-dimensions. Using available potential energy surfaces and coupling matrix elementsobtained from multireference ab initio calculations, five non-adiabatically coupled electronic states of1P symmetry have been included in the dynamical simulations. The collision has been studied in thelow energy regime of 1-10 eV. The wavepacket...
-
1,3-alternate calix[4]arene-bonded silica stationary phases. Effect of calixarene skeleton substituents on the retention mechanism and column selectivity
PublicationFour novel 1,3-alternate calix[4]arene-bonded silica gel stationary phases possessing different aromatic and aliphatic substituents at the upper rim (CalixNph, CalixBph, CalixHex and CalixDdc) were prepared and structurally characterized. The comparison and selectivity of these phases was done by using alkylbenzenes, fatty acid p-bromophenacyl esters, aromatic positional isomers and polynuclear aromatic hydrocarbons as analytes....
-
Stripe order and magnetic anisotropy in the S=1 antiferromagnet BaMoP2O8
PublicationMagnetic behavior of yavapaiite-type BaMoP2O8 with the spatially anisotropic triangular arrangement of the S=1Mo4+ ions is explored using thermodynamic measurements, neutron diffraction, and density-functional band-structure calculations. A broad maximum in the magnetic susceptibility around 46 K is followed by the stripe antiferromagnetic order with the propagation vector k=(12,12,12) formed below TN≃21 K. This stripe phase is...
-
Relativistic two-dimensional hydrogen-like atom in a weak magnetic field
PublicationA two-dimensional (2D) hydrogen-like atom with a relativistic Dirac electron, placed in a weak, static, uniform magnetic field perpendicular to the atomic plane, is considered. Closed forms of the first- and second-order Zeeman corrections to energy levels are calculated analytically, within the framework of the Rayleigh–Schrödinger perturbation theory, for an arbitrary electronic bound state. The second-order calculations are...
-
Implementation of high-precision computation capabilities into the open-source dynamic simulation framework YADE
PublicationThis paper deals with the implementation of arbitrary precision calculations into the open-source discrete element framework YADE published under the GPL-2+ free software license. This new capability paves the way for the simulation framework to be used in many new fields such as quantum mechanics. The implementation details and associated gains in the accuracy of the results are discussed. Besides the "standard" double (64 bits)...
-
A general approach to study molecular fragmentation and energy redistribution after an ionizing event
PublicationWe propose to combine quantum chemical calculations, statistical mechanical methods, and photoionization and particle collision experiments to unravel the redistribution of internal energy of the furan cation and its dissociation pathways. This approach successfully reproduces the relative intensity of the different fragments as a function of the internal energy of the system in photoelectron–photoion coincidence experiments and...
-
Linear-scaling calculation of Hartree-Fock exchange energy with Non-orthogonal Generalised Wannier Functions
PublicationWe present a method for the calculation of four-centre two-electron repulsion integrals in terms of localised non-orthogonal generalised Wannier functions (NGWFs). Our method has been imple- mented in the ONETEP program and is used to compute the Hartree-Fock exchange energy component of Hartree-Fock and Density Functional Theory (DFT) calculations with hybrid exchange-correlation functionals. As the NGWFs are optimised in situ...
-
Charge Transfer, Complexes Formation and Furan Fragmentation Induced by Collisions with Low-Energy Helium Cations
PublicationThe present work focuses on unraveling the collisional processes leading to the fragmentation of the gas-phase furan molecules under the He+ and He2+ cations impact in the energy range 5–2000 eV. The presence of different mechanisms was identified by the analysis of the optical fragmentation spectra measured using the collision-induced emission spectroscopy (CIES) in conjunction with the ab initio calculations. The measurements of...
-
The importance of anchoring ligands of binuclear sensitizers on electron transfer processes and photovoltaic action in dye-sensitized solar cells
PublicationThe relatively low photon-to-current conversion efficiency of dye-sensitized solar cells is their major drawback limiting widespread application. Light harvesting, followed by a series of electron transfer processes, is the critical step in photocurrent generation. An in-depth understanding and fine optimization of those processes are crucial to enhance cell performance. In this work, we synthesize two new bi-ruthenium sensitizers...
-
Superconductivity and appearance of negative magnetocaloric effect in Ba1–xKxBiO3 perovskites, doped by Y, La and Pr
PublicationRecently, substantial attention is given to the bismuth-based perovskites for variety of electronic applications. The perovskites are used for quantum dots displays (QLED), photovoltaic systems and superconducting (HTS) devices. In this paper comprehensive studies of Ba1–xKxBi1–yREyO3 bismuth perovskites (REBKBO, RE = Y , La or Pr) are reported. Apart from structural anomalous behavior at low temperatures, the electronic properties...
-
Simulating propagation of coherent light in random media using the Fredholm type integral equation
PublicationStudying propagation of light in random scattering materials is important for both basic and applied research. Such studies often require usage of numerical method for simulating behavior of light beams in random media. However, if such simulations require consideration of coherence properties of light, they may become a complex numerical problems. There are well established methods for simulating multiple scattering of light (e.g....
-
Site-selective magnetic order of neptunium inNp2Ni17
PublicationWe present the results obtained by superconducting quantum interference device (SQUID) magnetometry, specific heat, and Mossbauer spectroscopy measurements carried out on Np2Ni17 polycrystalline samples. We show that long-range magnetic order, with a moment mu((2b)) similar to 2.25 mu(B), occurs below T-N = 17.5 K on the Np (2b) sites. A nontrivial situation is observed in that the other Np sites (2d) do not take part to the order...
-
Computational methods for calculation of binding free energy for ligand-receptor complexes
PublicationAccurate description of the molecular complexes energetic influence is required for understanding of many biological functions carried out by proteins. Therefore, estimation of binding free energy for ligand-receptor complexes is of highest importance for structure-based ligand design and drug discovery approaches.Experimental methods of determination of difference in Gibbs'es free energy have many limitations. Thus, computational...
-
Spontaneous electron emission vs dissociation in internally hot silver dimer anions
PublicationReferring to a recent experiment, we theoretically study the process of a two-channel decay of the diatomic silver anion (Ag2-), namely the spontaneous electron ejection giving Ag2 + e- and the dissociation leading to Ag- + Ag. The ground state potential energy curves of the silver molecules of diatomic neutral and negative ion were calculated using proper pseudo-potentials and atomic basis sets. We also estimated the non-adiabatic...
-
Kriging Models for Microwave Filters
PublicationSurrogate modeling of microwave filters’ response is discussed. In particular, kriging is used to model either the scattering parameters of the filter or the rational representation of the filter’s characteristics. Surrogate models for these two variants of kriging are validated in solving a microwave filter optimization problem. A clear advantage of surrogate models based on the rational representation over the models based on scattering...
-
Universal construction of genuinely entangled subspaces of any size
PublicationWe put forward a simple construction of genuinely entangled subspaces – subspaces supporting only genuinely multipartite entangled states – of any permissible dimensionality for any number of parties and local dimensions. The method uses nonorthogonal product bases, which are built from totally nonsingular matrices with a certain structure. We give an explicit basis for the constructed subspaces. An immediate consequence of our...
-
Method for universal detection of two-photon polarization entanglement
PublicationDetecting and quantifying quantum entanglement of a given unknown state poses problems that are fundamentally important for quantum information processing. Surprisingly, no direct (i.e., without quantum tomography) universal experimental implementation of a necessary and sufficient test of entanglement has been designed even for a general two-qubit state. Here we propose an experimental method for detecting a collective universal...
-
Objectivity in the non-Markovian spin-boson model
PublicationObjectivity constitutes one of the main features of the macroscopic classical world. An important aspect of the quantum-to-classical transition issue is to explain how such a property arises from the microscopic quantum theory. Recently, within the framework of open quantum systems, there has been proposed such a mechanism in terms of the so-called spectrum broadcast structures. These are multipartite quantum states of the system...
-
Monitoring of the Process of System Information Broadcasting in Time
PublicationOne of the problems of quantum physics is how a measurement turns quantum, noncopyable data, towards copyable classical knowledge. We use the quantum state discrimination in a central system model to show how its evolution leads to the broadcasting of the information, and how orthogonalization and decoherence factors allow us to monitor the distance of the state in question to the one perfectly broadcasting information, in any...
-
Swapping Space for Time: An Alternative to Time-Domain Interferometry
PublicationYoung's double-slit experiment [1] requires two waves produced simultaneously at two different points in space. In quantum mechanics the waves correspond to a single quantum object, even as complex as a big molecule. An interference is present as long as one cannot tell for sure which slit is chosen by the object. The more we know about the path, the worse the interference. In the paper we show that quantum mechanics allows for...
-
Theoretical study of the photoelectron spectrum of ethyl formate: Ab initio and density functional theory investigation
PublicationThe first ionization energy and associated photoelectron spectrum of ethyl formate are investigated with quantum chemistry calculations. The geometries, harmonic vibrational frequencies and first ionization energy are computed at the Hartree-Fock (HF) and at the second order Moller-Plesset perturbation theory (MP2). Moreover, accurate ionization energies are obtained with the Coupled-Cluster theory including singles and doubles...
-
Hydroperoxyl radical and formic acid formation from common DNA stabilizers upon low energy electron attachment
Publication2-Amino-2-(hydroxymethyl)-1,3-propanediol (TRIS) and ethylenediaminetetraacetic acid (EDTA) are key components of biological buffers and are frequently used as DNA stabilizers in irradiation studies. Such surface or liquid phase studies are done with the aim to understand the fundamental mechanisms of DNA radiation damage and to improve cancer radiotherapy. When ionizing radiation is used, abundant secondary electrons are formed...
-
Hybrid Analysis of Structures Composed of Axially Symmetric Objects
Publication— A hybrid method for the scattering problems in shielded and open structures is presented. The procedure is based on the combination of body-of-revolution involving finite-element methods with impedance matrix formulation and the mode-matching technique, which can be utilized for the analysis of structures with axially symmetrical scatterers. In order to confirm the validity and efficiency of the proposed approach, a few examples...
-
Hidden Tensor Structures
PublicationAny single system whose space of states is given by a separable Hilbert space is automatically equipped with infinitely many hidden tensor-like structures. This includes all quantum mechanical systems as well as classical field theories and classical signal analysis. Accordingly, systems as simple as a single one-dimensional harmonic oscillator, an infinite potential well, or a classical finite-amplitude signal of finite duration...
-
Characterizing the Performance of <span class="sc">xor</span> Games and the Shannon Capacity of Graphs
PublicationIn this Letter we give a set of necessary and sufficient conditions such that quantum players of a two-party xor game cannot perform any better than classical players. With any such game, we associate a graph and examine its zero-error communication capacity. This allows us to specify a broad new class of graphs for which the Shannon capacity can be calculated. The conditions also enable the parametrization of new families of games...
-
Finite-difference time-domain analyses of active cloaking for electrically-large objects
PublicationInvisibility cloaking devices constitute a unique and potentially disruptive technology, but only if they can work over broad bandwidths for electrically-large objects. So far, the only known scheme that allows for broadband scattering cancellation from an electrically-large object is based on an active implementation where electric and magnetic sources are deployed over a surface surrounding the object, but whose ‘switching on’...
-
Konzetrationslöschung durch Energieübertragung bei der Lumineszenz von Lösungen
PublicationThe absorption spectra and quantum yields of the fluorescence of rhodamine 6 G are investigated in two different water-glycerol mixtures as a function of the rhodamine concentration. The observed concentration quenching is attributed to the formation of rhodamine dimers and the decrease in quantum yield is compared with theoretical concepts about concentration quenching by energy transfer to the dimers.
-
Increased Certification of Semi-device Independent Random Numbers using Many Inputs and More Postprocessing
PublicationQuantum communication with systems of dimension larger than two provides advantages in information processing tasks. Examples include higher rates of key distribution and random number generation. The main disadvantage of using such multi-dimensional quantum systems is the increased complexity of the experimental setup. Here, we analyze a not-so-obvious problem: the relation between randomness certification and computational requirements...