Wyniki wyszukiwania - BazTech

1

Właściwości czasowo-rozdzielcze słabych międzycząsteczkowych wiązań wodorowych C-H···F

Polańska Marta, Rodziewicz Paweł

Wiadomości Chemiczne

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2023

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[Z] 77, 9-10

899--919

EN

The hydrogen bond is one of the most important and interesting phenomena in nature. In this publication we will shed light on the discovery of hydrogen bond and a time evolution of its definition in the last 100 years. Both structural and spectroscopic parameters of the hydrogen bond will be discussed. A special focus will be given to the latest IUPAC definition of the hydrogen bond and its consequences to scientific research. The main aim of this study is to highlight theoretical studies based on first principles calculations and molecular dynamics simulations which not only support experimental results but also provide parameters which are crucial to understand the nature of hydrogen bonds. Particular attention will be given to methods and theoretical ideas used in the computational studies of hydrogen bonds. Utilizing static DFT/ab initio calculations and molecular dynamics simulations enables comparison of different binding energies and studying time evolution of the hydrogen-bonded molecular system on the atomistic level. We will discuss time-resolved properties of weak intermolecular hydrogen bonds, using as an example C-H···F containing model systems, namely F3CH*(HF)n molecular complexes and (F3CH)2-4 aggregates.

2

Do we still need a laboratory to study advanced oxidation processes? A review of the modelling of radical reactions used for water treatment

Wacławek Stanisław

Ecological Chemistry and Engineering. S

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2021

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Vol. 28, nr 1

11--28

EN

Environmental pollution due to humankind’s often irresponsible actions has become a serious concern in the last few decades. Numerous contaminants are anthropogenically produced and are being transformed in ecological systems, which creates pollutants with unknown chemical properties and toxicity. Such chemical pathways are usually examined in the laboratory, where hours are often needed to perform proper kinetic experiments and analytical procedures. Due to increased computing power, it becomes easier to use quantum chemistry computation approaches (QCC) for predicting reaction pathways, kinetics, and regioselectivity. This review paper presents QCC for describing the oxidative degradation of contaminants by advanced oxidation processes (AOP, i.e., techniques utilizing •OH for degradation of pollutants). Regioselectivity was discussed based on the Acid Blue 129 compound. Moreover, the forecasting of the mechanism of hydroxyl radical reaction with organic pollutants and the techniques of prediction of degradation kinetics was discussed. The reactions of •OH in various aqueous systems (explicit and implicit solvation) with water matrix constituents were reviewed. For example, possible singlet oxygen formation routes in the AOP systems were proposed. Furthermore, quantum chemical computation was shown to be an excellent tool for solving the controversies present in the field of environmental chemistry, such as the Fenton reaction debate [main species were determined to be: •OH < pH = 2.2 < oxoiron(IV)]. An ongoing discussion on such processes concerning similar reactions, e.g., associated with sulphate radical-based advanced oxidation processes (SR-AOP), could, in the future, be enriched by similar means. It can be concluded that, with the rapid growth of computational power, QCC can replace most of the experimental investigations related to the pollutant’s remediation in the future; at the same time, experiments could be pushed aside for quality assessment only.

3

Właściwości wewnątrzcząsteczkowych wiązań wodorowych w wybranych N-tlenkach pochodnych chinoliny

Jezierska Aneta, Panek Jarosław J., Błaziak Kacper

Wiadomości Chemiczne

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2019

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[Z] 73, 1-2

75--95

EN

In the current article we would like to summarize our research shedding light onto properties of intramolecular hydrogen bonds present in N-oxide quinoline derivatives. The compounds for the current study were chosen to contain diverse types of hydrogen bonds. Therefore, in the current study we analyze three kinds of hydrogen bonding and their properties. It is well known, that the presence of intramolecular hydrogen bonds stabilizes conformations of molecules. Substituent effects (inductive and steric) influence the strength of the H-bonding as well as its features. Moreover, the intramolecular hydrogen bond in the studied N-oxides belongs to the family of resonance assisted hydrogen bonds (RAHB). Our short overview presents the summary of results obtained for twelve N-oxides of quinoline derivatives. Quantum-chemical simulations were performed on the basis of static models (classical DFT and MP2 approaches) as well as ab initio molecular dynamics (Car-Parrinello MD). The metadynamics method was applied to reproduce the maps of free energy for the motion of the bridged proton. The computations were performed in the gas and in the crystalline phases. Electronic ground state is a natural framework in which chemical compounds exist most of the time. However, in many chemical species we observe a spontaneous internal reorganization of their chemical bonds and atoms e.g. proton transfer phenomenon and the appearance of tautomeric forms already in the ground state. Therefore, it was interesting to investigate some N-oxides in the excited electron state knowing that they exhibit excited- state-induced proton transfer (ESIPT effect). At the end of the article we draw some conclusions related to the intramolecular H-bond properties present in the discussed N-oxides of quinoline derivatives.

4

Badania strukturalne cyklicznych β-aminoketonów z wykorzystaniem metod obliczeniowych i analizy NMR

Sidorowicz K., Łaźny R.

Chemik

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2015

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Vol. 69, nr 7

401--410

PL

Przestrzenna konfiguracja na atomie azotu w cyklicznych β-aminoketonach powoduje, że związki te mogą występować w dwóch stereoizomerycznych formach, w których podstawniki na tym atomie mogą przyjmować orientację aksjalną lub ekwatorialną w stosunku do pierścienia piperydonu. Stereochemia N-podstawionych bicyklicznych β-aminoketonów była badana za pomocą metod eksperymentalnych i teoretycznych, m.in.: spektroskopia NMR, spektroskopii mikrofalowa, rentgenografii strukturalnej i obliczeń DFT.

EN

Because of pyramidal configuration of the nitrogen atom, tropanes, granatanes, and their derivatives can exist in two stereoisomeric forms, in which N-substituents can be oriented axial or equatorial with respect to the piperidone ring. The N-invertomer stereochemistry of N-substituted bicyclic β-amino ketones has been investigated using experimental, and theoretical methods, such as NMR, microwave spectroscopy, crystallography, and DFT calculations.

5

Density Functional Theory Study Of The Interaction Of Hydroxyl Groups With Iron Surface

Nunomura N., Sunada S.

Archives of Metallurgy and Materials

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2015

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Vol. 60, iss. 2A

931--933

EN

The electronic interaction of hydroxyl groups with Fe(100) surface is modelled using a density functional theory (DFT) approach. The adsorption energies and structures of possible adsorption sites are calculated. According to our calculations of the adsorption energies, the interaction between oxygen atom of OH species and surface iron atom is shown to be strong. It is likely to be due to the interaction of the lone-pair electrons of oxygen and the 3d orbital electrons of iron atom. At low coverage (0.25ML), the most favorable adsorption sites are found to be two-fold bridge sites, and the orientation of the O-H bond is tilted to the surface normal. Further, the adsorption energy is found to be decreasing with the increasing OH group coverage.

PL

Wzajemne oddziaływanie elektronowe grup hydroksylowych na powierzchni Fe(100) modelowano stosując metodę teorii funkcjonału gęstości (ang. density functional theory; DFT). Dokonano obliczeń energii adsorpcji oraz struktury potencjalnych centrów adsorpcji. Na podstawie otrzymanych wyników stwierdzono, że pomiędzy atomem tlenu grupy OH, a powierzchnią atomu żelaza występuje silne oddziaływanie. Jest to prawdopodobnie spowodowane oddziaływaniem wolnej pary elektronowej tlenu z elektronami atomu żelaza na orbitalach 3d. Przy niskim poziomie pokrycia (0,25 ML), najbardziej uprzywilejowane centra aktywne stanowią podwójne pozycje mostkowe, a orientacja wiązania O-H jest prostopadła do powierzchni. Ponadto energia adsorpcji zmniejsza się wraz ze wzrostem ilości grup OH na powierzchni.

6

Stability phase diagram of the Ir-Pt solid solution - numerical modelling from first principles

Woźniakowski A., Deniszczyk J.

Journal of Medical Informatics & Technologies

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2013

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Vol. 22

265--269

EN

First principles based numerical methods are used to determine the phase stability diagram of the Ir–Pt solid solution with A1-type crystal structure. Ising-like cluster expansion formalism was used to construct the lattice Hamiltonian. Phase diagram was calculated with the use of Monte Carlo simulations. Miscibility gap in this system was predicted. Calculated consolute temperature (TC) is about 1250 K at 50% of platinum when excess vibrational contribution to the free energy was included. The result is in good quantitative agreement with experimental data.

7

Density functional theory based modeling of the corrosion on iron surfaces

Nunomura N., Sunada S.

Archives of Metallurgy and Materials

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2013

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Vol. 58, iss. 2

321--323

EN

In order to understand the first steps of the aqueous corrosion of iron, we have performed density functional theory (DFT) based calculations for water molecules and pre-covered oxygen on iron surface. The surface structure is modeled by iron atomic layer and vacuum region, and then oxygen atom and water molecules are displaced on the surface. Self consistent DFT calculations were performed using a numerical atomic orbital basis set and a norm-conserve pseudopotential method. According to our calculations, with increasing surface oxygen coverage, the iron surface is found to be not activated, which leads to a feeble adsorption of water molecules on iron surface. Our results show that the surface covered oxygen exerts an influence on the adsorption of water molecules on iron surface.

PL

W celu zrozumienia początkowych etapów korozji żelaza w środowisku wodnym wykonaliśmy obliczenia dla cząsteczek wody i powierzchni żelaza pokrytej tlenem przy użyciu teorii funkcjonału gęstości (DFT). Model struktury powierzchni zawiera warstwę atomów żelaza i obszar próżni, a następnie atomy tlenu i cząsteczki wody rozmieszczane na powierzchni. Obliczenia DFT wykonano w zastosowaniem bazy orbitali atomowych i metody pseudopotencjału zachowania normy (norm-conserve). Zgodnie z wynikami naszych obliczeń, ze wzrostem pokrycia powierzchni przez tlen, powierzchnia żelaza nie jest aktywowana, co prowadzi do słabej adsorpcji cząsteczek wody na powierzchni żelaza. Nasze wyniki wskazują, ze powierzchnia pokryta tlenem wywiera wpływ na adsorpcje cząsteczek wody na powierzchni żelaza.

8

Structural and mechanical properties of ZnTe in the zincblende phase

Soykan C., Ozdemir Kart S., Cagin T.

Archives of Materials Science and Engineering

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2010

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Vol. 46, nr 2

115-119

EN

Purpose: The aim of this work investigate to the structural and mechanical properties of ZnTe in the B3 structure, using the ab initio method based on Density Functional Theory (DFT). Design/methodology/approach: The Vienna ab initio Simulation Package (VASP) has been used to perform the electronic structure calculations. The projector-augmented wave formalism (PAW) implemented in this package leads to very accurate result comparable to other all-electron methods. The electronic exchange and correlation functions are treated within DFT by using generalized gradient approximation. Findings: The lattice parameter, bulk modulus, it's pressure derivative and the elastic stiffness coefficients are calculated. Our results for the structural parameters and the elastic constants at the equilibrium phase are in good agreement with the available experimental and other theoretical studies. We have also investigated the pressure dependence of mechanical properties for ZnTe in the structure of B3 to see this effect. Research limitations/implications: These compounds are convenient for many technological applications because of they have direct energy band gaps and property of light emitters at room temperature. Practical implications: These compounds used to many technological applications, such as solid state laser devices, photovoltaic devices, solar cells, remote control systems, thin films, transistors, THz emitter, detector and imaging systems etc. Originality/value: In this work, determination of structural and mechanical properties of ZnTe in the B3 structure at high pressures will lead to new technological applications of these materials.

9

Badania nowych materiałów metodami adsorpcyjnymi z zastosowaniem do analizy danych metod DFT i ROA (Aparat ASAP 2010, Micromeritics)

Kaleńczuk R. J.

Chemia i Inżynieria Ekologiczna

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2002

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Vol. 9, nr 5/6

611-615

PL

Przedstawiono zastosowanie pakietów DFT (Density Functional Theory- teoria funkcjonału gęstości) i ROA (Rate of Adsorption - szybkość adsorpcji) do analizy danych doświadczalnych procesu niskotemperaturowej adsorpcji azotu pochodzących z aparatu ASAP dla przypadku badań nad nową rodziną węgli aktywnych preparowanych z węgla kamiennego.

EN

The case of use of DFT (density functional theory) and ROA (rate of adsorption) tools for analysis of adsorption experimental data obtained with ASAP 2010 instrument (Micromeritics) during the study on a new technology for active carbon production has been presented.