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    Computation of Two-Center Coulomb Integrals Over Slater-Type Orbitals Using Elliptical Coordinates
    (John Wiley & Sons Inc, 2003) Özmen, Ayhan; Karakaş, Aslı; Atav, Ülfet; Yakar, Yusuf
    A general analytic formula is obtained for the two-center Coulomb integrals over Slater-type orbitals in elliptical coordinates. Finite series expansions are used in the evaluation of the radial part of the integrals. The analytic formula is expressed in terms of a product of the well-known auxiliary functions A,(p) and B,(p) and incomplete gamma functions. Recursive relations for the computer evaluation of these functions are given as well. The recursive relations are stable and our computer results are in good agreement with the benchmark values given in the literature.
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    Novel Salts of 2,4-Diaminoquinazoline: Searching for Materials for Second Harmonic Generation Based on A Promising Polarizable Cation
    (Springer/Plenum Publishers, 2012) Fridrichova, Michaela; Nemec, Ivan; Cisarova, Ivana; Tesarova, Nad'a; Nemec, Petr; Karakaş, Aslı; Kahraman, Nihal; Taşer, Mehmet
    The chloride and l-tartrate salts of the 2,4-diaminoquinazolinium(1+) were prepared and characterized by both X-ray diffraction and infrared spectroscopy. The potential of the 2,4-diaminoquinazolinium(1+) cation as a building block for materials for nonlinear optics was assessed using quantum mechanical computations. Both 2,4-diaminoquinazolinium(1+) chloride dihydrate (a = 7.2121(1) , b = 8.0105(2) , c = 18.6157(5) , beta = 92.493(1)A degrees, V = 1074.46(4) (3), Z = 4, R = 0.0305 for 4605 observed reflections) and 2,4-diaminoquinazolinium(1+) l-tartrate dihydrate (a = 7.2899(2) , b = 11.9508(2) , c = 13.4183(3) , beta = 92.375(2)A degrees, V = 1168.00(5) (3), Z = 2, R = 0.0367 for 4761 observed reflections) belong to the monoclinic space group P2(1). They are stable, non-hygroscopic, colorless and exhibit non-zero SHG efficiency for powdered samples. Two novel non-centrosymmetric salts of 2,4-diaminoquinazolinium(1+) were prepared and thoroughly characterized during the search for materials for the second harmonic generation.
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    Study on the Second Order Optical Properties of N-(2,4-dichloro)-salicylaldimine
    (Verlag der Zeitschrift fur Naturforschung, 2005) Karakaş, Aslı; Ünver, Hüseyin; Elmalı, Ayhan; Svoboda, Ingrid
    N-(2,4-Dichloro)-salicylaldimine was synthesized, characterized by elemental analysis, FT-IR, and UV-visible spectroscopy, and its crystal structure was determined. The title compound is almost planar and contains short intramolecular O-H... N hydrogen bonds [O1-N1 2.601(1) Å]. It remains transparent in the visible region and has solvatochromic behavior in the UV region in the range 198 349 nm, implying non-zero microscopic first hyperpolarizability. The ab-initio quantum mechanical calculations (finite field second-order Møller Plesset perturbation theory) of the studied compound have been carried out to compute the electric dipole moment (?) and the first hyperpolarizability (?) values. The ab-initio results also show that this ligand might have microscopic nonlinear optical behavior with non-zero values.
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    Syntheses, Structures and Second-order Nonlinear Optical Behavior of (E)-N-(4-Nitrobenzylidene)-3,4-Dimethylaniline and (E)-N-(3-Nitrobenzylidene)-3,4-Dimethylaniline
    (Verlag Z Naturforsch, 2010) Ünver, Hüseyin; Karakaş, Aslı; Durlu, Tahsin Nuri
    (E)-N-(4-Nitrobenzylidene)-3,4-dimethylaniline (1) and (E)-N-(3-nitrobenzylidene)-3,4-dimethylaniline (2) have been synthesized, and their crystal structures have been determined by X-ray diffraction analysis. Linear optical characteristics have been evaluated experimentally using UV/Vis spectroscopy and theoretically using the configuration interaction (CI) method. The maximum one-photon absorption (OPA) wavelengths of the studied compounds are shorter than 450 nm, giving rise to good optical transparency in the visible and near IR regions. The ab initio quantum-mechanical calculations (finite field second-order Moller-Plesset perturbation theory) of the investigated molecules have been carried out to compute the electric dipole moment (mu) and the first hyperpolarizability (beta) values. The ab initio results suggest that the title compounds might have microscopic second-order nonlinear optical (NLO) behavior with non-zero values.