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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 Linear and Nonlinear Refractive Index Changes in Spherical Quantum Dot(2011) Çakır, B.; Yakar, Y.; Özmen, A.In this study, refractive index changes associated with in- tersubband transitions in a spherical quantum dot. GaAs/Al, Gal-As, have been theoretically calculated in the presence of impurity. In this regard, the effect of dot radius, stoichiometric ratio, impurity and in- cident optical intensity on the refractive index changes have been in- vestigated for the transitions between higher energy states, i.e., Is-1p, 1p-1d and 1d-lf. The results show that these parameters have a great influence on the refractive index changes.Öğe Vibrational Spectral and Quantum Chemical Investigations of Tert-Butyl-Hydroquinone(ELSEVIER, 2012) Dereli, Ö.; Erdoğdu, Y.; Güllüoğlu, M. T.; Türkkan, E.; Özmen, A.; Sundaraganesan, N.The Fourier transform infrared (FT-IR) and micro-Raman spectra of tert-butyl-hydroquinone were recorded in the region 4000-400 cm(-1) and 4000-50 cm(-1), respectively. Conformational space was scanned with molecular mechanic simulations. All other calculations were performed by B3LYP/6-311G++(d,p) level of theory. The molecular structure and vibrational frequencies of the title compound were calculated and compared with experimental spectra. Theoretical vibrational spectra of the title compound were interpreted by means of TEDs. Predicted electronic absorption spectrum of tert-butylhydroquinone from TD-DFT calculation was analyzed and compared with the experimental UV-visible spectrum.
