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Öğe Calculation of Rotation Coefficients for Overlap Integrals Over Arbitrary Atomic Orbitals(1997) Guseinov, I. I.; Atav, Ü.; Özmen, A.; Yüksel, H.; Aliyeva, T. H.Rotation coefficients for overlap integrals over arbitrary atomic orbitals are calculated by two methods. In the first method, using binomial coefficients, directly calculated Clebsch-Gordan coefficients and normalized associated Legendre functions were used to obtain the rotation coefficients. Whereas in the second method recursively calculated Clebsch-Gordan coefficients and normalized associated Legendre functions were used. The methods are compared with respect to cpu time requirement and accuracy. It was concluded that it is appropriate to use the first method for angular momentum quantum numbers up to 40 and for larger quantum numbers the second method is more advantageous.Öğe Computation of Clebsch-Gordan and Gaunt Coefficients Using Binomial Coefficients(ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS, 1995) Guseinov, I.I.; Özmen, A.; Atav, U.; Yüksel, H.Using binomial coefficients the Clebsch-Gordan and Gaunt coefficients were calculated for extremely large quantum numbers. The main advantage of this approach is directly calculating these coefficients, instead of using recursion relations. Accuracy of the results is quite high for quantum numbers l(1) and l(2) up to 100. Despite direct calculation, the CPU times are found comparable with those given in the related literature.Öğe Computation of Overlap Integrals Over Slater-Type Orbitals Using Auxiliary Functions(JOHN WILEY & SONS INC, 1998) Guseinov, I. I.; Özmen, A.; Atav, U.; Yüksel, H.Analytical expressions through the binomial coefficients and recursive relations are derived for the expansion coefficients of overlap integrals in terms of a product of well-known auxiliary functions A(k) and B-k. These formulas are especially useful for the calculation of overlap integrals for large quantum numbers. Accuracy of the computer results is satisfactory for the values of quantum numbers up to 50 and for the arbitrary values of screening constants of atomic orbitals and internuclear distances.Öğe EPR Study of Gamma-Irradiated Single Crystal 4-Phenylsemicarbazide(Pergamon-Elsevier Science Ltd, 2010) Sayın, U.; Türkkan, E.; Dereli, Ö.; Yüksel, H.; Birey, M.Single crystals of 4-phenylsemicarbazide (4PSC) were investigated using an electron paramagnetic resonance (EPR) technique, with gamma irradiation of the crystals at different orientations in the magnetic field between temperatures of 120 and 450 K, and the spectra were found to be temperature independent. Taking into consideration the chemical structure and the experimental spectra of the irradiated single crystal 4PSC, we assumed that one or more paramagnetic species were produced, each having an unpaired electron delocalized in the phenyl ring. Pursuant to this assumption, six possible radicals were modeled using the B3LYP/6-311+G(d) level of density-functional theory. EPR parameters were calculated for these modeled radicals using the B3LYP method and TZVP basis set. The calculated hyperfine coupling constants were used as starting points for simulations. The experimental and simulated spectra for each of the three crystallographic axes were well matched for the modeled radical R6. We thus identified the R6 (C6H5NH) radical as a paramagnetic species produced in 4PSC. The experimental g-factor and hyperfine coupling constants of the C6H5NH radical were found to be anisotropic, with the average values g = 2.00431, a(NH)(N(8)) = 8.85 G, a(NH)(H(9)) = 16.85 G, a(o,p)(H(14,16,20)) = 6.47 G, and a(m)(H(18,19)) = 2.80 G.
