Wyniki wyszukiwania - BazTech

1

Effect of zirconium doping on the mechanical properties of W1−x Zr x B2 on the basis of first‑principles calculations and magnetron sputtered films

Maździarz Marcin, Psiuk Rafał, Krawczyńska Agnieszka, Lewandowska Malgorzata, Mościcki Tomasz

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 4

art. no. e193, 2022

EN

Potentially superhard polymorphs, hP6-P6/mmc-WB and hP3-P6/mmm-WB, were thoroughly analyzed with zirconium doping in the range of x=0-25%, within the framework of the first-principles density functional theory, from both a structural and a mechanical point of view. The obtained results were subsequently compared with the properties of material deposited by the magnetron sputtering method. All predicted structures are mechanically and thermodynamically stable. Theoretical calculations suggest a decrease in hardness and fracture toughness of the hP6 phase with zirconium doping but no such effect on the hP3 phase. It was observed that an additional defect in the analyzed structure significantly weakens the hP6 phase but strengthens the hP3 phase. The deposited films are characterized by greater hardness but lower fracture toughness. The results of experiments show that not only is solid solution hardening responsible for strengthening the predicted new material but also the change in microstructure, the Hall–Petch effect and vacancies.

2

Recent Results on Computational Molecular Modeling of The Origins of Life

Mayen Juan Francisco Carrascoza, Błażewicz Jacek

Foundations of Computing and Decision Sciences

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2020

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Vol. 45, No. 1

35--46

EN

In the last decade of research in the origins of life, there has been an increase in the interest on theoretical molecular modeling methods aimed to improve the accuracy and speed of the algorithms that solve the molecular mechanics and chemical reactions of the matter. Research on the scenarios of prebiotic chemistry has also advanced. The presented work attempts to discuss the latest computational techniques and trends implemented so far. Although it is difficult to cover the full extent of the current publications, we tried to orient the reader into the modern tendencies and challenges faced by those who are in the origins of life field.

3

Symulacje ab-initio warstwy grafenowej wykorzystywanej w detektorze IR

Woźny J., Ruta Ł., Lisik Z.

Elektronika : konstrukcje, technologie, zastosowania

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2016

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Vol. 57, nr 10

31--32

PL

W artykule przedstawione zostały wyniki symulacji ab-initio z wykorzystaniem oprogramowania MedeA VASP warstwy grafenowej w obecności wybranych materiałów wykorzystywanych w konstrukcji detektora podczerwieni. Symulacje miały za zadanie odpowiedzieć, czy i w jaki sposób zmieniają się parametry warstwy grafenowej w obecności SiO₂ i Al₂O₃. Ocenie poddany został kształt pasm energetycznych.

EN

The article presents the results of ab-initio simulations by the means of Medea VASP tool of graphene layer in the presence of selected materials used in the production of infrared detector. The simulations have been performed to answer whether and how the parameters of the graphene sheet may change in the presence of SiO₂ and Al₂O₃. Assessment has been done on the basis of the energy bands shape. Graphene is a material that has opened new perspectives in the design of electronic devices and launched studies on various 2D materials. The correct determination of the parameters of graphene must take into account the conditions in which the graphene layer operates. Within this work we show preliminary the free layer graphene band structure. Obtaining a correct shape of the energy bands is possible by the means of DFT approach when appropriate mesh in the k domain is used: Δk = 0.05 1/Ä. Simulations of the graphene layer placed and SiO₂ and between SiO₂ and Al₂O₃ confirmed that the shape of band structure remains untouched at Dirac point and p-type doping of graphene layer has been observed for simulated structures.

4

Predictive study of structural, electronic, magnetic and thermodynamic properties of XFeO3 (X = Ag, Zr and Ru) multiferroic materials in cubic perovskite structure: first-principles calculations

Moulay N., Ameri M., Azaz Y., Zenati A., Al-Douri Y., Ameri I.

Materials Science Poland

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2015

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Vol. 33, No. 2

402--413

EN

The full potential linear-muffin-tin-orbital method within the spin local density approximation has been used to study the structural, electronic, magnetic and thermodynamic properties of three multiferroic compounds of XFeO3 type. Large values of bulk modulus for these compounds have been obtained, which demonstrates their hardness. The calculated total and partial density of states of these compounds shows a complex of strong hybridized 3d and 4d states at Fermi level. The two degenerate levels e(g) and t(2g) clearly demonstrate the origin of this complex. We have also investigated the effect of pressure, from 0 GPa to 55 GPa, on the magnetic moment per atom and the exchange of magnetic energy between the ferromagnetic and antiferromagnetic states. For more detailed knowledge, we have calculated the thermodynamic properties, and determined heat capacity, Debye temperature, bulk modulus and enthropy at different temperatures and pressures for the three multiferroic compounds. This is the first predictive calculation of all these properties.

5

Ab Initio Study of AuTe2 Cluster

Su Rong Q. M., Liu F. M.

Polish Journal of Chemistry

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2009

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Vol. 83, nr 2

285-292

EN

The geometries of the lowest-lying isomers of small AuTe2 cluster are determined through the MP2 method. The aspect of gold-telluride and telluride-telluride interaction, the electron correlation and relativistic effects on geometry and stability were investigated at the different theoretical levels of electron correlation. The results show that the electron correlation and relativistic effects are responsible not only for telluride-telluride attraction but also for additional gold-telluride interaction. Both effects are essential for determining the geometry and relative stability of coin age metal telluride compound AuTe2 cluster.

6

The Protonation Equili rium and Decomposition of Amino- and Hydroxyphosphonates, Phos phine Ox ides and Phosphonic Acid

Doskocz M., Gancarz R., Roszak S.

Polish Journal of Chemistry

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2007

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Vol. 81, nr 11

2013-2021

EN

Protonation states of amino and hydroxyl phosphoroorganic derivatives have been studied. Based on the presented calculations we can state that mono- and di-protonated species on nitrogen are dominating states in solution. The protonation on phosphoryl oxygen occurs only as an effect of dynamic equilibrium between protonated species. The double and tripple protonation lead to very strong acid and thus such states are rather not present even in strong acidic media.

7

Patterns of Counter-Rotating Ring Currents in TwoValence Isomers of Corazulene

Lillington M., Fowler P., Diudea M.

Polish Journal of Chemistry

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2007

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Vol. 81, nr 5-6

653-662

EN

Current-density maps computed in the ipsocentric approach are presented for two isomeric polycyclic systems: corazulene (1) in which four azulene units are fused around a central square, and cornaphthalene (2) in which the azulene units of 1 are replaced by naphthalenes. Both show a strong central paratropic current on the square. Whereas 1 presents concentric counter-rotating rim-and-hub currents, 2 shows a ‘Clar-like’ structure of diatropic currents on the four outer hexagonal rings. Partition of the total current into orbital contributions, both canonical and localized, gives a clear rationale for the appearance of the maps.

8

Carbon encapsulated iron nanowires

Ramirez R., Weissmann M., Garcia G., Kiwi M.

Materials Science Poland

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2006

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Vol. 24, No. 4

883--890

EN

A study of the structural and magnetic properties of carbon encapsulated iron nanowires is presented. The influence of carbon presence on iron magnetic ordering by means of an ab initio computer simulation has been studied. For wires tightly encapsulated, i.e. with large ratio of wires and nanotubes radii, the presence of carbon strongly alters Fe magnetic configuration of free standing wires, in some cases yielding antiferromagnetic ordering. The energy differences between ferromagnetic and antiferromagnetic phases are small enough to allow their coexistence in a nanowire, which is in agreement with the experimental evidence of exchange-bias in such systems.

9

The Pronotation Site in Aminophosp

Doskocz M., Miziak P., Gancarz R.

Polish Journal of Chemistry

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2005

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Vol. 79 / nr 3

547-552

EN

The protonation equilibria in aminophosphonates: protonation on nitrogen vs phosphoryl oxygen has been calculated. The calculated energy differences explain satisfactory experimentally observed tendency toward nonstability of aminophoshonates in acidic media.

10

Complexes of Adenine with Metal Ions: Stability and Excited States

Rubina A., Rubin Y., Sorokin V., Shukla M., Leszczyński J.

Polish Journal of Chemistry

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2005

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Vol. 79 / nr 12

1873-1882

EN

Molecular geometry optimizations and excited state energy calculations were performed for the N9H and N7H tautomers of adenine (Ade) and their complexes with selected transition metal ions (Cu+, Cu2+, Zn2+ and Ag+). The ground state geometry optimizations were carried out at the HF and UHF (for open-shell metal ions) levels, while transition energies were calculated using the configuration interaction involving single excited configurations (CIS method). Single point ground state energy calculations were also performed at the full MP2 (UMP2 for open-shell systems) level. The 6-31+G(d,p) basis set was used for all but Ag+ containing complexes for which the LANL2DZ basis set was used. Experimental UV-spectra of adenine complexes with Cu2+ and Ag+ metal cations in the water solution were also obtained. These spectra show red-shift of approximately 1000 cm-1 in comparison with that of the adenine. The analysis of the first electronic singlet - * transition energies suggests that metal ion binding to the N1 or N7 atomic sites of adenine generally leads to the red-shift, while the binding at the N9 site leads to blue shift of the absorption maximum of complexes. The most probable binding site for the Cu+ and Zn2+ ions is found to be the N7 atomic site of the N9H tautomer of adenine. Divalent copper Cu2+ ion would bind at the N1 site. Co-existence of the two forms of adenine complexes with silver ion ([N9H-Ade-AgN1]+, and [N9H-Ade-AgN7]+) is also revealed.

11

Vibrational properties and thermochemistry from first principles

Wolf W., Sticht J., Mavromaras A., Leblanc B., Saxe P., Wimmer E.

Materials Science Poland

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2005

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Vol. 23, No. 2

365--373

EN

The simulation of vibrational properties and finite temperature effects based on ab initio calculation of phonons within the direct approach is discussed. The implementation of the approach within an automated computational framework is outlined, and applications in rather diverse fields are demonstrated: phonon dispersion of GaAs, Kohn anomaly in Niobium, rattling modes in thermoelectric skutterudites, reaction enthalpies and formation enthalpies of hydrides and hydrogen storage materials, phase transformations, surface reconstruction of Si( 111), and adsorption of CO molecules on a Ni( 001) surface.

12

The growing importance of computations in materials science. Current capabilities and perspectives

Wimmer E.

Materials Science Poland

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2005

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Vol. 23, No. 2

325--345

EN

Materials scientists are facing unprecedented challenges in many areas, such as energy conversion and storage, microelectronics, telecommunication, display technologies, catalysis, and structural materials. Experimental methods generate increasing amounts of data. New computational methods, high-performance computer hardware, and powerful software environments are evolving rapidly. As a result, the importance of computational materials science is growing. The following cases illustrate the current capabilities: computed thermochemical and mechanical properties of metal hydrides show trends in the heats of formation and the hydrogen-induced softening of elastic moduli; a study of the effect of impurities on the strength of a Ni grain boundary reveals hydrogen as an embrittler and boron as a strengthener; ab initio phonon calculations for hydrogen impurities in aluminum show a temperature-dependent site - preference; the screened-exchange approach predicts accurate energy band gaps of semiconductors; a computational screening of hydro-desulphurization catalysts points to new combinations. The major current challenges for computational materials science include more accurate total energies, unified methods to deal with multi-phase systems, e. g., solid/liquid, novel approaches to determine complex kinetic processes, and novel concepts to bridge the atomistic and the macroscopic scales.

13

Obliczenia ab initio metodą FP-LAPW w inżynierii Materiałowe

Koleżyński A.

Informatyka w Technologii Materiałów

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2004

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T. 4, Nr 1-2

48-55

PL

Celem prezentowanej pracy było pokazanie możliwości wykorzystania obliczeń ab initio, przeprowadzanych przy pomocy dostępnych obecnie komputerów osobistych klasy PC, do analizy własności typowych, powszechnie stosowanych materiałów. Na przykładzie kryształu BaTiO3 o strukturze kubicznej i programu WIEN97 wykorzystującego przybliżenie zlinearyzowanych stowarzyszonych fal płaskich, z pełnym potencjałem krystalicznym (Full Potential Linearized Augmented Plane Wave Method), pokazano metodę optymalnego doboru parametrów obliczeniowych i przeprowadzono przykładowe obliczenia. Dla trzech różnych potencjałów wymiany - korelacji, obliczono energię całkowitą kryształu, energię wiązania, parametry równania stanu i moduł sprężystości objętościowej. Wyniki porównano z danymi eksperymentalnymi i wartościami ab initio, uzyskanymi innymi metodami. Pokazano dużą zgodność zarówno z danymi eksperymentalnymi, jak i wynikami obliczeń kwantowych. Ponieważ metoda FP-LAPW jest uznawana za jedną z najbardziej precyzyjnych metod umożliwiających obliczanie struktury pasmowej i cechuje ją brak założeń co do kształtu potencjału krystalicznego, wyniki otrzymane za pomocą programu WIEN97 umożliwiają prowadzenie szczegółowej analizy wielu fizykochemicznych własności krystalicznych ciał stałych (rodzaje i własności wiązań chemicznych, przepływ ładunku, mapy gęstości elektronowej, gradient pola elektrycznego, tensor polaryzacji, krzywe dyspersji, gęstości stanów itd.). Zastosowanie programu WIEN97 do szczegółowej analizy ferroelektrycznego przejścia fazowego w krysztale tytanianu baru, zarówno z punktu widzenia gęstości elektronowej jak też struktury pasmowej, z uwzględnieniem stabilności wyników obliczeń, zostanie przedstawione szerzej w odrębnej publikacji (Koleżyński, 2004).

EN

In this paper, the overview and practical aspects of ab initio calculations using WIEN97 FP-LAPW package are presented. A step by step process of parameters setting and refinement is described in details. The results of the calculations for cubic barium titanate crystal structure, for three different exchange-correlation potentials (CA-LDA, PW-GGA and PBE-GGA) are presented. The obtained binding energy and equilibrium cell parameters from Murnaghan equation of state are compared to experimental and literature data (ab initio calculations results by means of other - DFT and HF methods). The obtained results show good agreement with both experimental and ab initio data

14

Ferroelektryczne przejście fazowe w krysztale tytanianu baru. Obliczenia ab initio metodą FP-LAPW. Cz. I. Analiza rozkładu gęstości elektrycznej

Koleżyński A.

Informatyka w Technologii Materiałów

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2004

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T. 4, Nr 4

144-153

PL

Celem prezentowanej pracy, była próba symulacji ferroelektrycznego przejścia fazowego w krysztale tytanianu baru za pomocą obliczeń ab initio, wykonanych z wykorzystaniem pakietu FP-LAPW (Full Potential Linearized Augmented Plane Wave) Wien97. Dokonano analizy zmian składowych energii całkowitej (energii elektronów rdzenia i elektronów walencyjnych, energii potencjalnej), zmian populacji elektronów w sferach muffin-tin i w obszarze międzywęzłowym, oraz szczegółowej analizy rozkładów gęstości elektronowej w komórce elementarnej, ze szczególnym uwzględnieniem zmian jednowymiarowych rozkładów gęstości w wybranych kierunkach (wiązania Ti-O, Ba-O, Ti-Ba oraz kierunki (110)), pozwalającej na zbadanie zmian przestrzennego rozkładu ładunku w komórce elementarnej w trakcie przemiany prowadzącej do obniżenia symetrii kryształu od symetrii regularnej Fm-3m paraelektrycznej wysokotemperaturowej fazy tytanianu baru, do symetrii tetragonalnej P4mm i równocześnie do polaryzacji ładunku i pojawienia się własności ferroelektrycznych. Przedstawione dane potwierdzają nasze wcześniejsze wyniki (Tkacz-Śmiech i in., 2000,2003; Koleżyń-ski, Tkacz-Śmiech, 2004) wskazujące na istotną rolę lokalizacji ładunku w obszarze pomiędzy tytanem i tlenem w kierunku osi z i tworzenia się wiązania n pomiędzy elektronami 3 d tytanu i 2p tlenu, oraz znikomy wpływ oddziaływań atomów tlenu i tytanu z barem na przemianę fazową i pojawienie się własności ferroelektrycznych. W drugiej części pracy zaprezentowane zostaną wyniki symulacji przejścia fazowego z punktu widzenia wpływu deformacji komórki elementarnej i obniżenia symetrii na strukturę pasmową, charakter poszczególnych pasm, populacje elektronowe w poszczególnych pasmach oraz indywidualnie wybranych punktach sieci odwrotnej o wysokiej symetrii, a także wpływ ferroelektrycznego przejścia fazowego na zmiany funkcji gęstości stanów. Dodatkowo przedstawiona zostanie dyskusja otrzymanych wyników i charakteru oraz własności wiązań chemicznych występujących w krysztale tytanianu baru, w świetle teorii orbitali molekularnych.

EN

In this paper, the results of the ferroelectric phase transition simulation in barium titanate, by means of ab initio calculations, using FP-LAPW (Full Potential Linearized Augmented Plane Wave) method (Wien97 program) are presented. The paper consists of two parts - in the first one here, the detailed analysis of the calculated energy eigenvalues, potential energy terms, electron populations and electron density distribution together with their changes during gradual crystal cell deformation from regular Fm-3m paraelectric, to P4mm tetragonal ferroelectric barium titanate phase are analyzed. The obtained results are in agreement with our previous crystal-chemical analysis (Tkacz-Śmiech et al. 2003) and show the importance of the charge localization process in region of Ti-O bond along z axis, which leaves the Ti-O bonds lying in xy plane almost intact. The second part of this paper will be focused mainly on the influence of the ferroelectric phase transition on the changes of the band structure, bands character and DOS and their connection with molecular picture of chemical bond in barium titanate crystal.

15

Phase equilibria in Ni-Al-Cr-Co-W-Re system: modelling and experiments

Bursik J.

Archives of Metallurgy and Materials

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2004

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Vol. 49, iss. 3

505-518

EN

Ordering processes typical for Ni-base superalloys were studied in a multicomponent system Ni-Al-Cr-Co-W-Re by means of computer modelling using Monte Carlo method combined with ab initio calculations. Complementary calculations were also run using ThermoCalc software for modelling of thermodynamic equilibria. Together with modelling, experiments were carried out by means of analytical scanning and transmission electron microscopy after a long term annealing at high temperatures typical for application of Ni-based superalloys. The microstructure of equilibrium states was characterized as regards the phase constitution and chemical composition of phases. The comparison of results of applied methods is given.

PL

Proces porządkowania, typowy dla nadstopów na bazie niklu, był obiektem badań w układzie wieloskładnikowym Ni-Al-Cr-Co-W-Re przy pomocy modelowania komputerowego stosując metodę Monte Carlo w połaczeniu z obliczeniami ab initio. Równoległe obliczenia prowadzono również za pomocą pakietu thermoCalc. Doswiadczenia przeprowadzono stosując metode elektronowej mikroskopii skaningowej i transmisyjnej. Na podstawie wyników badań scharakteryzowano zarówno równowagową mikrostrukturę stopów jak również ich skład chemiczny i fazowy. Porównano wyniki badań róznymi metodami.

16

First-principles calculation of the Cu-Li phase diagram

Van de Walle A., Moser Z., Gąsior W.

Archives of Metallurgy and Materials

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2004

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Vol. 49, iss. 3

535-544

EN

We present first-principles calculations of the solid-state portion of the Cu-Li phase diagram based on the cluster expansion formalism coupled with the use of (i) bond length-dependent transferable force constants and lattice dynamics calculations to model of vibrational disorder and (ii) lattice gas Monte Carlo simulations to model configurational disorder. These calculations help settle the existence of additional phases in the Cu-Li phase diagram that have been postulated, but not yet clearly established. Our calculations predict the presence of at least one additional phase and the associated predicted phase transitions are consistent with our electrochemical measurements, which exhibit clear plateaus in the electromotive force-composition curve.

PL

Prezentujemy obliczenia ab initio wykresu równowagi fazy stałej układu Cu-Li. Obliczenia opierają się na formalizmie Cluster ezpansion (CE) realizowanym przy: (i) zastosowaniu stałych siłowych zależnych od długości wiązania oraz obliczeń dynamiki sieci do modelowania wibracyjnego stanu nieuporządkowania: (ii) zastosowaniu symulacji Monte Carlo gazu sieciowego do modelowania stanu nieuporządkowania konfiguracyjnego. Obliczenia te umożliwiły wykazanie dodatkowych faz w układzie równowagi układu Cu-Li, które były wcześniej postulowane, lecz nie potwierdzone. Nasze obliczenia przewidują obecność co najmniej jednej dodatkowej fazy, a postulowane przejścia fazowe sa zgodne z naszymi badaniami elektrochemicznymi, które wykazały wyraźne załamania w zależnościach sił elektromotorycznych względemstężenia.

17

Infrared Matrix Isolation Studies and Ab Initio Calculations of Acetohydroxamic Acid

Sałdyka M., Mielke Z.

Polish Journal of Chemistry

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2003

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Vol. 77 / nr 11

1587-1598

EN

The infrared absorption spectra of acetohydroxamic acid (CH3CONHOH) and its deuterated analogue (CH3CONDOD) isolated in argon and nitrogen matrices have been recorded for the first time. The infrared spectra prove that this molecule exists as the keto tautomer with intramolecular hydrogen bond in solid argon and nitrogen. Theoretical studies of the structure and spectral characteristics of the acetohydroxamic acid molecule, carried out on both MP2 and B3LYP levels with the 6-311++G(2d,2p) basis set, are in accordance with the experimental data.

18

An ab initio Post SCF Study on Stacking Interactions of 8-Oxo-9-methylguanine with Four Canonical DNA Bases

Cysewski P., Czyżnikowska-Balcerak Z., Szefler B.

Polish Journal of Chemistry

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2003

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Vol. 77 / nr 10

1287-1300

EN

Stacking properties of 8-oxo-9-methylguanine interacting with all four canonical nucleic acid bases were studied and compared to dimers formed by unmodified guanine. The impact of twist angle and base-base separation distance on the stacked dimers energies were analyzed based on MP2/6-31G*(d=0.25) quantum chemistry and Amber molecular mechanics single point calculations. Besides, solvent affects were taken into account within PCM formalism. Presented data lead to the conclusion that 8-oxo-9-methylguanine has significantly different stacking properties compared to standard guanine. Although the dimers stabilization energies are similar for standard and modified 9-methylguanine structural properties are significantly diverse. The most stable dimers formed by 8-oxo- 9-methyl-G are characterized by different conformations compared to canonical 9- methylguanine. This may lead to complete alteration of stacking abilities. For example, 8-oxo-9-methyl-G if paired with 9-methyl-G exhibits strong stacking repulsion in the twist region, for which 9-methylguanine/9-methylguanine dimer has major attraction. The most stable stacking pair is formed by 8-oxo-9-methylguanine with 9-methylguanine, while the least stable one corresponds to 8-oxo-9-methylguanine/1-methylcytosine and 9-methylguanine/1-methylcytosine pairs. Besides, significant changes of stacked complexes polarities are observed, especially in case of pairs containing methylated pyrimidines. Polarities of dimer formed by two 9-methylated purines are much less sensitive to the environment but dipole moments of 9-methylpurine/1-methylpyrimidine stacking pairs are significantly altered by taking into account solvent effects. The observed differences in stacking properties between standard and modified guanine are related mainly to charge redistribution rather than direct interactions of O8 oxygen. The correlation energies of stacking dimers are very high and are main source of pairs stabilization. Both 9-methylguanine and 8-oxo-9-methylguanine are characterized by similar values of correlation energy.

19

Density functional studies of the cobaltous acid dimer : preliminary results

Gajewski G., Latajka Z., Ratajczak H.

Bulletin of the Polish Academy of Sciences. Chemistry

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2002

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Vol. 50, No. 2

131-137

EN

The structure, interaction energy and vibrational frequencies of the hydrogen bonded cobaltous acid monomer and dimer were investigated at the B3LYP level with the CEP-31G** basis set. The cobaltous acid forms stable cyclic dimer with the dimerization energy of about -14 kcal/mol. The structural parameters of monomers are strongly perturbed upon dimerization, and the vibrational spectra are predicted to show large vibrational shifts compared with the monomer spectra.

20

Conformational analysis of 1,2,4,5-tetroxane

Jorge N., Gomez-Vara M., Romero J. R., Castro E. A.

Bulletin of the Polish Academy of Sciences. Chemistry

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2002

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Vol. 50, No. 3

387-395

EN

Different theoretical procedures are applied to make a conformational study of the 1,2,4,5-tetroxane molecule: AMI semi-empirical method, ab initio RHF method at the 3-21+G and 6-311+G(d,p) basis set levels and B3LYP density functional method at the same basis set levels. The molecular stability is analyzed on the basis of different stereo-electronic and symmetry features. There is a general agreement between these methods and all of them predict the chair conformation to be the most stable conformer.