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Two-Dimensional Charge-Transfer Molecules for Poled Polymer Applications
Published in Seizo Miyata, Hiroyuki Sasabe, Poled Polymers and their Applications to SHG and EO Devices, 2020
Tatsuo Wada, Takashi Isoshima, Tetsuya Aoyama, Yadong Zhang, Liming Wang, Jean-Luc Brédas, Keisuke Sasaki, Hiroyuki Sasabe
In searches for multifunctional NLO-phores we have developed various carbazole derivatives which possess both photoconductivity and second-order nonlinear optical response [5]. Carbazole compounds are well known to exhibit good hole transporting properties and their photocarrier generation efficiency can be sensitized by formation of CT complexes [6]. The carbazole molecule has an isoelectronic structure of diphenylamine, that is, electron-donative nature as shown in Figure 2. Therefore, the introduction of electron-withdrawing groups in the 3 and/or 6-position induces intracharge-transfer. Depending on the electron-affinity of acceptor groups, the additional CT bands are superimposed in a visible region. Various substituent groups were systematically examined in different positions such as R1, R2 and/or R3 in Figure 2. Although 9-substituent group does not significantly affect the electronic property of carbazole rings, the hydrogen bonding in 9-hydroxyethyl substituent plays the important role of generating noncentrosymmetric packing of carbazole molecules in a crystal [7].
Functional Properties of High Entropy Alloys
Published in T.S. Srivatsan, Manoj Gupta, High Entropy Alloys, 2020
Anirudha Karati, Joydev Manna, Soumyaranajan Mishra, B.S. Murty
Stolze and co-workers [167] have found correlations between lattice parameter (Figure 14.9a), valence electron count (Figure 14.9b), and TC in the case of these high entropy alloy superconductor, while Rohr and co-workers [165] and Ishizu and Kitawaga [166] have deduced the impact of both valence electron count and mixing entropy (Figure 14.10a and b) on the “cocktail effect” of the critical temperature in these superconductors. Rohr and Cava [168] have also focused on isoelectronic substitution and aluminum doping in the (TaNb)67(ZrHfTi)33 system and have concluded that isoelectronic substitution and the resulting change in TC depends upon the group the element are in, that overall valence electron count dominates over disorder in the lattice, and that crystallinity of above high entropy alloys depends upon the extent of aluminum doping and the overall TC of these systems. And Vrtnik and co-workers [160] have investigated the effect of annealing time on overall microstructure, how it was being influenced by the overall minimization of mixing enthalpy and maximization of mixing entropy, and how that has an overall influence on the superconductivity in these samples.
Magnetism and Transport in DMS Quantum Dots
Published in Evgeny Y. Tsymbal, Igor Žutić, Spintronics Handbook: Spin Transport and Magnetism, Second Edition, 2019
Joaquín Fernández‑ Rossier, Ramón Aguado
In this section, we briefly review the spin interactions relevant to Mn-doped quantum dots. We first consider a II-VI material and then discuss briefly the differences in the case of a III-V material. As a substitutional impurity of the group II atom, Mn is an isoelectronic impurity. The electrons in the half-filled d shell can be considered localized in the Mn atom and, in agreement with the Hunds rule, they form a spin S = 5/2. In the model, electrons and holes in the confined levels of the quantum dot are described in the kp effective mass approximation. We consider quantum dots small enough as to have a sizable quantization of their energy spectrum.
Theoretical spectroscopy in the early days of digital computing – an homage to Sigrid D. Peyerimhoff
Published in Molecular Physics, 2020
Experiments on the C molecule by Ballik and Ramsay [22] had found a state to be favoured over the state by less than 0.1 eV. Earlier experimental and theoretical studies on the question of the ground state of the isoelectronic CN ion were not conclusive. As this question was potentially interesting for astronomical searches, Bruna et al. [23] set out for a very systematic investigation how the atomic orbital basis, the choice of the reference space and the configuration selection threshold influence the energy splitting between these states. They emphasise the importance of a multi-reference CI treatment for the energy splitting and conclude that the is the electronic ground state with a - splitting of the order of only 0.1–0.15 eV. It should take nearly 40 years before rotational spectra under cryogenic conditions conclusively confirmed that CN occupies a electronic ground state [24]. Pablo Bruna's major contributions to the field of theoretical spectroscopy in the 1970ies and 1980ies are summarised in [25].
Distributed Gaussian orbitals for molecular calculations: application to simple systems
Published in Molecular Physics, 2020
Stefano Battaglia, David Bouet, Alexis Lecoq, Stefano Evangelisti, Noelia Faginas-Lago, Thierry Leininger, Andrea Lombardi
The first case that will be discussed is given by two isoelectronic systems, i.e. the helium atom and the H− negative ion. The Helium atom is a very compact system, due to the closed-shell character and the occupation of orbital only. It can be described by a relatively small number of distributed function. On the other hand, because of the excess of negative charge, the H− system has a very diffuse wavefunction, and thus requires a large number of distributed Gaussians for an accurate description. Notice that this large number could be substantially reduced at the price of using more diffuse distributed Gaussians, i.e. by taking a smaller value of . However, since our philosophy is to use a unique type of Gaussians for the distributed functions, we did not explore this possibility.
Cross sections for electron collision with pyridine [C5H5N] molecule
Published in Molecular Physics, 2019
Czesław Szmytkowski, Sylwia Stefanowska, Natalia Tańska, Bożena Żywicka, Elżbieta Ptasińska-Denga, Paweł Możejko
Present absolute grand -total cross sections (TCS) were measured at electron-impact energies ranging from 0.6 to 300 eV using the linear electron-transmission method. To our knowledge, the experimental TCS data below 1 eV are not available in the literature. The observed low-energy features in our TCS were explained based on findings of previous experiments [8-12] and computations [19,20]. The current electron-scattering TCS results for the pyridine [CHN] molecule were then compared to experimental TCS data [28,29] for its isoelectronic six-membered ring counterpart benzene [CH]; the substituent effect is discussed. We also present elastic (ECS) and ionisation (ICS) cross sections for pyridine and its two halogenated derivatives (2-chloropyridine and 2-bromopyridine) computed at intermediate and high electron-impact energies in the additivity rule approximation and the binary-encounter-Bethe approach, respectively.