Grzegorz Mazur

Jagiellonian University, Cracovia, Lesser Poland Voivodeship, Poland

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Publications (16)27.5 Total impact

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    ABSTRACT: A novel method of investigating the multicenter bonding patterns in molecular systems by means of the so-called Electron Density of Delocalized Bonds (EDDB) is introduced and discussed. The EDDB method combines the concept of Jug's bond-order orbitals and the indirect ("through-bridge") interaction formalism and opens up new opportunities for studying the interplay between different atomic interactions as well as their impact on both local and global resonance stabilization in systems of conjugated bonds. On several illustrative examples we demonstrate that the EDDB approach allows for reliable quantitative description of diverse multicenter delocalization phenomena (with special regard to evaluation of the aromatic stabilization in molecular systems) within the framework of a consistent theoretical paradigm.
    Physical Chemistry Chemical Physics 08/2014; · 3.83 Impact Factor
  • Grzegorz Mazur, Piotr Petelenz, Michał Slawik
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    ABSTRACT: Owing to the peculiar structure of oligothiophene crystals, their low-energy b-polarized spectra are dominated by the contributions from charge transfer states almost free from Frenkel state admixtures, offering a unique opportunity for in-depth studies of the former. Here, a simple model, rooted in the Mulliken theory of charge transfer transitions, is proposed to estimate the relevant transition dipole moments. For sexithiophene, the resultant estimate agrees with the value used in the recent detailed theoretical reproduction of the absorption and electroabsorption spectra, and is found to be consistent with other input parameters. The approach presented here is readily applicable for other one-component molecular crystals, providing a simple method to estimate the intrinsic transition dipoles of charge transfer configurations.
    Chemical Physics 03/2012; 397:92–97. · 1.96 Impact Factor
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    ABSTRACT: The recently introduced quadratic (two-electron) valence indices, ionic and covalent, derived from the Hartree–Fock finite-difference approach, are applied to selected organic and inorganic molecules to demonstrate their utility in monitoring chemical bonding patterns in molecular systems. The indices are defined in terms of differerences between simultaneous probabilities of finding two electrons on specified atoms, calculated from the molecular and separated-atom-limit (SAL) wave functions, respectively, in the UHF approximation. The total quadratic valence number represents the overall number of chemical bonds in the system under consideration; it is interpreted as the molecular expectation value of the difference operator of the molecular and SAL density operators. This interpretation leads to a new set of ionic atomic and diatomic valence components; these modified valence numbers are discussed using the two-orbital model in the UHF scheme. A new procedure is proposed for dividing the one-center contributions to the bond valences; it generates effective bond orders in qood agreement with chemical expectations. The new valence quantities are tested on selected typical molecules and prototype hydrogen-bonded dimers. A more extensive study has been carried out on small-ring propellanes, to examine changes in bond valences between bridgehead atoms in selected systems. Key words: chemical valence: UHF difference approach; chemical bond: two-electron model; bond multiplicities; ionic/covalent bond components; propellanes: valence study.
    Canadian Journal of Chemistry 02/2011; 74(6):1121-1130. · 0.96 Impact Factor
  • Anna Styrcz, Janusz Mrozek, Grzegorz Mazur
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    ABSTRACT: A novel, neural network controlled, dynamic evolutionary algorithm is proposed for the purposes of molecular geometry optimization. The approach is tested for selected model molecules and some molecular systems of importance in biochemistry. The new algorithm is shown to compare favorably with the standard, statically parametrized memetic algorithm.
    Applied Mathematics and Computer Science. 01/2011; 21:559-566.
  • Michael Seth, Grzegorz Mazur, Tom Ziegler
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    ABSTRACT: An implementation of time-dependent density functional theory (TDDFT) energy gradients into the Amsterdam density functional theory program package (ADF) is described. The special challenges presented by Slater-type orbitals in quantum chemical calculation are outlined with particular emphasis on details that are important for TDDFT gradients. Equations for the gradients of spin-flip TDDFT excitation energies are derived. Example calculations utilizing the new implementation are presented. The results of standard calculations agree well with previous results. It is shown that starting from a triplet reference, spin-flip TDDFT can successfully optimize the geometry of the four lowest singlet states of CH2 and three other isovalent species. Spin-flip TDDFT is used to calculate the potential energy curve of the breaking of the C–C bond of ethane. The curve obtained is superior to that from a restricted density functional theory calculation, while at the same time the problems with spin contamination exhibited by unrestricted density functional theory calculations are avoided. KeywordsTime-dependent density functional theory–Analytical gradients–Slater-type orbitals–Spin-flip
    Theoretical Chemistry Accounts 01/2011; 129(3):331-342. · 2.14 Impact Factor
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    ABSTRACT: Dressed TDDFT method is applied to the calculations of low-lying electronic excited states of selected linear polyenes and α,ω-diphenylopolyenes. It is shown that proper accounting for doubly excited configurations is necessary to correctly describe excitation energies and geometrical structure of the 21Ag state in these systems. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011
    International Journal of Quantum Chemistry 09/2010; 111(4):819 - 825. · 1.17 Impact Factor
  • Computing and Informatics. 01/2010; 29:989-1000.
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    Grzegorz Mazur, M. Makowski
    Computing and Informatics 01/2009; 28:115-125. · 0.25 Impact Factor
  • Grzegorz Mazur, Radosław Włodarczyk
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    ABSTRACT: Dressed Time-Dependent Density Functional Theory (Maitra et al., J Chem Phys 2004, 120, 5932) is applied to selected linear polyenes. Limits of validity of the approximation are briefly discussed. The implementation strategy is described. Results for the 2(1)B(u) and 2(1)A(g) states of selected linear polyenes are presented and compared with accessible experimental and theoretical results.
    Journal of Computational Chemistry 09/2008; 30(5):811-7. · 3.84 Impact Factor
  • Grzegorz Mazur
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    ABSTRACT: Convergence of the Self-Consistent Polarization Field (SCPF) method of polarization energy calculations for organic molecular materials is analysed. Use of the Conjugate Gradients method for solving the SCPF equations is proposed. Efficiency of both the original and the newly proposed approach is compared for selected model systems. Brief discussion of the factors influencing the performance of Krylov-space-based methods for polarization energy calculations is presented.
    Journal of Computational Chemistry 05/2008; 29(6):988-93. · 3.84 Impact Factor
  • Grzegorz Mazur, Piotr Petelenz, Michał Slawik
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    ABSTRACT: A three-dimensional analog of the Merrifield model is proposed to study excitons in solid perylenetetracarboxylic dianhydride (PTCDA). Its relevant parameters are estimated by independent calculations, and finally determined by fitting the experimental absorption and electroabsorption spectra of PTCDA films; the optimum values obtained from the fit correspond well with the calculated values. The results justify description of PTCDA excitons within a one-dimensional model, as proposed in the literature. The calculated spectra are generally in good agreement with the experimental ones, with the exception of the directional properties of the electroabsorption signal. A possible reason for this discrepancy is suggested. Generally, the results highlight the prominent role of charge-transfer excitons in the electroabsorption spectrum of PTCDA by showing the experimental features that are difficult to explain without invoking these states. © 2003 American Institute of Physics.
    The Journal of Chemical Physics 01/2003; 118(3):1423-1432. · 3.12 Impact Factor
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    Grzegorz Mazur, Piotr Petelenz
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    ABSTRACT: The energies of charge transfer (CT) states of the perylenetetracarboxylic dianhydride (PTCDA) crystal are evaluated by means of the Fourier transform (FT) and self-consistent polarization field (SCPF) methods. For the nearest-neighbour CT state the results support the estimates of other authors, based on the fit of the electro-absorption spectrum. The calculations also suggest that, owing to the peculiar structure of the PTCDA crystal, other CT states are located in the same energy range, which should be taken into account in future extensions of the existing theoretical models.
    Chemical Physics Letters 01/2000; · 2.15 Impact Factor
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    Piotr Petelenz, Grzegorz Mazur
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    ABSTRACT: The Merrifield model of electronic excitations in a linear molecular crystal is applied to investigate the relation between the bound electron–hole pairs (charge transfer excitons) and the corresponding continuum of unbound states. It is demonstrated that, contrary to the conventional explanation, the difference of 0.2–0.3 eV between the electric and optical band gap observed for polyacene crystals is a consequence of charge delocalization rather than lattice relaxation. The results also suggest that in some molecular crystals and polymers, moderate structural disorder may strengthen the photoconductive response instead of suppressing it, which suggests a new strategy in the search for efficient photoconductors.
    Synthetic Metals 01/2000; 109(1):73-77. · 2.11 Impact Factor
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    Journal of Molecular Structure (Theochem). 01/2000; 527:91-102.
  • Piotr Petelenz, Grzegorz Mazur
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    ABSTRACT: The observed difference of 0.2–0.3 eV between the optical and electric band gap in organic solids was commonly attributed to vibrational relaxation. The recently calculated values [I.V. Brovchenko, Chem. Phys. Lett. 278 (1997) 355] of the lattice relaxation energy in the vicinity of a charge carrier or a charge-transfer state never exceed 0.02–0.03 eV, demonstrating that the conventional rationalization of the difference is no longer tenable. An alternative explanation is proposed where the difference is interpreted in terms of charge delocalization and the past controversies are attributed to inconsistencies in treating this contribution to energy.
    Chemical Physics Letters 01/1999; · 2.15 Impact Factor
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    Grzegorz Mazur, Tom Ziegler
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    ABSTRACT: TD-DFT based methodology for calculating energy gradients with respect to the position of nuclea of molecules in excited states is pre- sented. It allows for exploring excited state geometries by locating energy minima as well as transition states of photochemical reactions. Despite an enormous success in dealing with ground state proper- ties, for a long time DFT could not be rigorously applied to excited states. This has recently changed with the development of time de- pendent density functional theory (TDDFT)(Casida, 1995). TDDFT has now become the methodology of choice for studying excitation en- ergies of large systems. However, work on the calculations of excited states energy gradients with respect to nuclea positions has started only recently (Caillie and Amos, 1999, Caillie and Amos, 2000), and the methodology is not yet in widespread use. We have developed energy gradients of excited states in a form suitable for implementation in ADF(van Gisbergen, 1999). While the basic outline of the work follows to large extent Ref. (Caillie and Amos, 1999, Caillie and Amos, 2000) the presented theory is augmented to make use of optimization techniques present in the ADF code, such as frozen core approximation and linear scaling.

Publication Stats

75 Citations
27.50 Total Impact Points

Institutions

  • 1999–2014
    • Jagiellonian University
      • • Department of Computational Methods in Chemistry
      • • Department of Theoretical Chemistry
      Cracovia, Lesser Poland Voivodeship, Poland
  • 2010
    • Japan Science and Technology Agency (JST)
      Edo, Tōkyō, Japan