Yazar "Ertuerk, M." seçeneğine göre listele

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    Application of combined Hartree-Fock-Roothaan theory to atoms with an arbitrary number of closed and open shells of any symmetry
    (Springer Wien, 2007) Guseinov, Israfil Isa; Mamedov, B. A.; Ertuerk, M.; Aksu, H.; Sahin, E.
    The applicability of a combined open-shell Hartree-Fock theory of atomic-molecular and nuclear systems to the states of a single configuration which has the arbitrary symmetry of open shells is explicitly demonstrated by calculations based on the combined Hartree-Fock-Roothaan equations for atoms. As examples of an application of the combined theory using single-zeta Slater-type basis sets, the calculations have been performed for the lowest states of the lowest and excited electronic configurations of carbon and nitrogen atoms containing one-, two- and three-open shells. For the case of single-open shells for carbon and nitrogen atoms, the double-zeta basis-set calculations are also presented. The results of computer calculations for the orbitals, kinetic and total energies, linear combination coefficients and virial ratios are given.
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    Towards Multireference Equivalents of the HEAT Thermochemical Protocol
    (Wiley, 2025) Coskun, M.; Koehn, A.; Ertuerk, M.
    This study systematically evaluates the performance of internally contracted multireference coupled cluster (icMRCC) wave functions constructed using a full-valence complete active space reference as an alternative electronic structure method within the high-accuracy extrapolated ab initio thermochemistry (HEAT) protocol, thereby assessing the accuracy of icMRCC and exploring its potential for highly accurate thermochemical predictions. By substituting single-reference wavefunctions with multireference (MR) alternatives, we aim to capture complex electron correlation effects, particularly in systems with strong static correlations. Using a benchmark dataset of 22 small first-row compounds, we compare the accuracy of different icMRCCSD(T) methodologies with both single-reference their counterparts and experimental data. Our results align with prior findings, confirming that the intrinsic error of the icMRCCSD(T){4}(F )method remains well below the chemical accuracy threshold (similar to 4 kJ mol(-1)) for thermochemical properties, particularly for atomization energies of molecules with up to 18 correlated electrons. The results underscore the potential of the methods for creating a multireference framework as a high-precision tool for thermochemical applications.
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    Öğe
    Use of Noninteger n-Slater Type Orbitals in Combined Hartree-Fock-Roothaan Theory for Calculation of Isoelectronic Series of Atoms Be to Ne
    (Wiley-Blackwell, 2009) Guseinov, Israfil Isa; Ertuerk, M.
    The ground state calculations in the combined Hartree-Fock-Roothaan approach are performed for the neutral and the first 20 cationic members of the isoelectronic series of atoms from Be to Ne using noninteger n-Slater type orbitals. For the total energies obtained, only a small deviation has been found. At the same time, the size of the present noninteger n-Slater type orbitals is smaller than that of the usual extended integer n-Slater functions in literature. All of the nonlinear parameters are fully optimized. The relationship between optimized parameters and atomic number Z is also investigated. For each atom, the total energies are given in tables. (C) 2008 Wiley Periodicals, Inc. Int J Quantum Chem 109: 176-184, 2009