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Öğe Alternating Heisenberg s =1/2 spin chain: Ferromagnetism versus antiferromagnetism(National Institute of Optoelectronics, 2006) Işik F.; Ekmekçi S.; Bayri A.Spin ladder systems containing CuCl3 and CuBr3 show very interesting magnetic behaviour, which are alternate Heisenberg chains with ferromagnetic and antiferromagnetic interactions. Since these systems contain triangles of magnetic centers, we developed a model based on non-interacting triangular units, which may be used for interpretation of magnetic measurements of these systems in some extreme limits. We took the Heisenberg model type interactions for magnetic center and used different types of exchange coupling between the neighbours. The results obtained from our approximations may be used in order to interpret the experimental magnetic measurements in KCuCl 3 and TlCuCl3 complexes and for the singlet-triplet transition temperature.Öğe Antiferromagnetic exchange interactions in asymmetrically bridged dinuclear Fe(III) complexes by phenoxo and metoxo groups: Magnetic field dependence of magnetisation(National Institute of Optoelectronics, 2010) Bayri A.; Bakir H.G.; Ekmekci S.In this study the antiferromagnetic interactions in recently synthesized dinuclear Fe(III) complex has been investigated in a magnetic field. For this purpose the magnetic moment of Fe(III) ions has been calculated in the vicinity of the magnetic field. Using the reported coupling constant, it was shown that the magnetic moment takes a ladder like behavior below a certain temperature. It was also shown that the saturation magnetization can be more easily obtained for small coupling constant.Öğe Antiferromagnetic ground states in some commonly known lattices(1997) Bayri A.Antiferromagnetism is a very interesting behaviours in some real materials and their alloys. It is important in high T c materials as well. The main reasons for antiferromagnetism are the kinetic exchange[1,2]. In this study, I will consider commonly known lattices in two or three dimensions. Using the Heisenberg model I will show that there are two systems: Frustrated and unfrustrated. In unfrustrated case the spin structure is unique and it involves ferromagnetism as well. However, in frustrated case the spin structure is not unique and it gives more than one spin orderings. This behaviours is very interesting since it causes a first order magnetic phase transition[3,4]. Finally, I will summarize that the simplier lattice (the square, the S.C. and B.C.C.) are unfrustrated and the complicated lattices (triangular, F.C.C. and H.C.P.) are frustrated.Öğe Benchmark Study of Computational Methods for Predicting Partition Coefficient of Chlormethiazole(TUBITAK, 2022) Serin S.; Bayri A.The present study contains the evaluations of lipophilicity estimation, HOMO-LUMO analysis, and electrostatic surface properties of Chlormethiazole molecule by using quantum chemical calculation techniques. All geometrical optimizations, energy and frequency calculations were carried out with six different basis sets by choosing the Hartree-Fock (HF) method and two different Density Functional Theory (DFT) functionals B3LYP and B3PW91. All calculations were repeated for the water and n-octanol phases by using SMD solvation model in order to investigate the solvent effect and also to obtain the Gibbs free energies of solvation that help to estimate partition coefficients. As a result, among the applied theoretical methods, the best agreement with the experimental logP value was obtained with the HF/6-31G(d,p) method. Also, it is concluded that the forecast performance of the computational methods decreases in the following order: HF> B3LYP> B3PW91. © 2022, TUBITAK. All rights reserved.Öğe Erratum: Magnetic behavior of trinuclear vanadium(II)-diamine complexes. Part 2. Large intramolecular antiferromagnetic exchange interactions in a triangular unit (Journal of Inorganic and Organometallic Polymers and Materials DOI: 10.1007/s10904-006-9036-9)(2007) Bayri A.; Sulu M.[No abstract available]Öğe Frustration and magnetic phase transition(1999) Gencer H.; Bayri A.; Ekmekçi S.[No abstract available]Öğe High probability of large orbital angular momentum contribution to the magnetic moment of cobalt(II) ion in newly reported macrocyclic complex containing amide, imine and secondary amine functions(Freund Publishing House Ltd, 2008) Bayri A.; Aytekin O.The magnetic moments of Co+2 complexes in newly reported macrocyclic complexes containing amide, imine, and secondary amine functions are investigated by a semi-theoretical approach for various geometrical situations. It is found that in order to obtain the observed room temperature magnetic moments, some of the parameters, related to the geometry of the complexes, should be varied in the magnetic Hamiltonian. The calculations and experiments obtained from the literature suggest that the environments of complexes are low field distorted octahedral. It is also suggested that while the probability of orbital contribution to the magnetic moment is high, the probability of ferromagnetic interactions between two cobalt(II) ions in a dimeric unit is quite low.
