International Journal of Quantum Chemistry

Cover image for Vol. 113 Issue 23

5 December 2013

Volume 113, Issue 23

Pages i–iv, 2489–2567

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      Cover Image, Volume 113, Issue 23 (pages i–ii)

      Version of Record online: 22 OCT 2013 | DOI: 10.1002/qua.24568

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      Zinc is an endogenous part of many proteins. Cadmium is a toxic metal, and replacing zinc in proteins is one of the reasons for its toxicity. Reliable estimates of the interaction energies between the ions and their ligands in proteins are desired, but difficult to obtain. Using small molecular models for Zn and Cd ligands in proteins, Emma Ahlstrand et al. on page 2554 calculate interaction energy curves with MP2 and DFT functionals, and compare them to CCSD(T) reference values. The results call for caution in applying DFT methods to metalloprotein model complexes, in particular at ion–ligand separations that are longer than the equilibrium distances.

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      Inside Cover, Volume 113, Issue 23 (pages iii–iv)

      Version of Record online: 22 OCT 2013 | DOI: 10.1002/qua.24569

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      Thermal effects improve bipolaron mobility and the overall system conductivity in conjugated polymers. When thermal effects are taken into account by Marcos Andre Pereira dos Santos, Wiliam Ferreira da Cunha, Pedro Henrique de Oliveira Neto, and Geraldo Magela e Silva on page 2540, the initially trapped bipolaron becomes able to respond to the external electric field applied. By releasing the upper bipolaron, a chain reaction takes place, affecting the other charge carriers. This results in a system with the highest possible conductivity, as all the quasi-particles are free to move after the collisional process.

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    1. Nonstationarity and related measures for time-dependent hartree–fock and multiconfigurational models (pages 2489–2505)

      Anatoliy V. Luzanov

      Version of Record online: 9 JUN 2013 | DOI: 10.1002/qua.24487

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      The energy–time uncertainty relation for driven quantum systems is interpreted in terms of the effective inverse “lifetime”, inline image, which refers to each instance of time. The dynamics of molecules in strong laser fields is analyzed with the help of inline image and an effective number of unpaired electrons.

    2. Understanding the oxidation of the tricarbon radical C3H: A reaction pathway survey (pages 2506–2513)

      Wei-Wei Zhu, Lin Jin, Zhong-Hua Cui, Shao-Wen Zhang and Yi-Hong Ding

      Version of Record online: 13 JUN 2013 | DOI: 10.1002/qua.24490

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      Recent observation of molecular oxygen in interstellar space illustrates the need for a mechanistic understanding of oxidation processes of various interstellar species. This manuscript studies the oxidation mechanism of the chainlike l-C3H (also detected in space) by molecular oxygen. It finds that the energetically most stable product is also kinetically the least stable. The overall reaction is found to be barrierless, and results in the abundant product C2H.

    3. Exploration on the structure, stability, and isomerization of planar CnB5 (n = 1−7) clusters (pages 2514–2522)

      Cheng Wang, Wenwen Cui, Jingling Shao, Xiaolei Zhu and Xiaohua Lu

      Version of Record online: 11 JUN 2013 | DOI: 10.1002/qua.24491

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      Carbon–boron binary compounds have been the topic of many experimental and theoretical studies because of their potential industry applications. In this work, the geometry, stability, nature of bonding, and isomerization of planar CnB5 (n = 1–7) clusters are investigated. Clusters with an even n have relatively higher stability. Two thermodynamically and kinetically stable isomers are found, which are expected to be experimentally detectable. Simulated spectra are expected to aid experimental efforts.

    4. Quantum chemical studies of novel 2′-4′ conformationally restricted antisense monomers (pages 2523–2533)

      Mallikarjunachari V. N. Uppuladinne, Vinod Jani, Uddhavesh B. Sonavane and Rajendra R. Joshi

      Version of Record online: 12 JUN 2013 | DOI: 10.1002/qua.24492

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      Antisense molecules can inhibit unwanted gene expression. The design of such molecules offers the capability to treat genetic diseases. This work carries out quantum chemical studies of specific antisense modifications at the monomer level. It finds good agreement with experimental findings, and an indirect relationship between quantum chemical descriptors and experimental data is established. This work is expected to be useful in antisense molecular design.

    5. High-precision calculations of the hyperfine constants and some selected transition energies for the low-lying 4S levels of the lithium atom (pages 2534–2539)

      Frederick W. King

      Version of Record online: 23 JUN 2013 | DOI: 10.1002/qua.24497

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      The hyperfine structure constants of selected excited quartet S levels of the lithium atom are determined using Hylleraas calculations. Such theoretical input is fundamental to the experimental investigation of the hyperfine structure of these systems.

    6. Influence of bipolaron density on the transport properties of thermalized organic conductors (pages 2540–2545)

      Marcos Andre Pereira dos Santos, Wiliam Ferreira da Cunha, Pedro Henrique de Oliveira Neto and Geraldo Magela e Silva

      Version of Record online: 26 JUN 2013 | DOI: 10.1002/qua.24501

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      Quasiparticles named bipolarons mediate charge transport in organic semiconductors. Devoid of an easy phenomenological model to understand the extended band picture, computational modeling of transport in organic semiconductors is needed. This work studies the influence of charge carrier density in polyacetylene. The quasiparticle interaction and temperature play a significant role in the system dynamics, resulting in a higher mobility with density. Good agreement with experimental data is found.

    7. Effective band gap reduction of titanium oxide semiconductors by codoping from first-principles calculations (pages 2546–2553)

      Xiaohui Yu, Tingjun Hou, Youyong Li, Xuhui Sun and Shuit-Tong Lee

      Version of Record online: 28 JUN 2013 | DOI: 10.1002/qua.24502

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      Titanium dioxide (TiO2) is a suitable photocatalyst for the degradation of environmental pollutants because of its strong catalytic activity, long-term chemical stability, low cost, and nontoxicity. Codoped TiO2 can exhibit a significantly narrowed band gap. In particular, (F+Fe)-codoped TiO2 could serve as a remarkably better photocatalyst with both a narrowing of the band gap, and relatively smaller formation energies than the other codoped TiO2 systems studied.

    8. Interaction energies between metal ions (Zn2+ and Cd2+) and biologically relevant ligands (pages 2554–2562)

      Emma Ahlstrand, Daniel Spångberg, Kersti Hermansson and Ran Friedman

      Version of Record online: 23 JUL 2013 | DOI: 10.1002/qua.24506

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      The interaction between group XII metal ions (Zn2+ and Cd2+) and amino acid residues plays an important role in biology. While Zn is a very common protein metal cofactor, similarly sized Cd is toxic. The interaction energy curves for these two ions and water or functional groups representing amino acid residues is computed using CCSD(T), MP2, and different DFT functionals in order to identify computationally cheaper, yet sufficiently accurate, approaches for modeling these systems.

    9. The influence of benzene rings on aromatic pathways in the porphyrins (pages 2563–2567)

      Rashid R. Valiev and Victor N. Cherepanov

      Version of Record online: 2 AUG 2013 | DOI: 10.1002/qua.24523

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      The influence of an external magnetic field on electrons of aromatic and anti-aromatic molecules is the reason for the appearance of diamagnetic and paramagnetic ring currents. The contribution of diamagnetic ring currents dominates in aromatic molecules, while that of paramagnetic ring currents dominates in anti-aromatic molecules. The paths of the currents within porphyrinoids macrocycles in their subrings are explored by using quantum chemical calculations.

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