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Correlation Potentials (correlation + potential)
Selected AbstractsTheoretical study in [C2H4,Tl]+ and [C2H2,Tl]+ complexesINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 1 2007Fernando Mendizabal Abstract We studied the attraction between [C2Hn] and Tl(I) in the hypothetical [C2Hn,Tl]+ complexes (n = 2,4) using ab initio methodology. We found that the changes around the equilibrium distance C,Tl and in the interaction energies are sensitive to the electron correlation potential. We evaluated these effects using several levels of theory, including Hartree,Fock (HF), second-order Møller,Plesset (MP2), MP4, coupled cluster singles and doubles CCSD(T), and local density approximation augmented by nonlocal corrections for exchange and correlation due to Becke and Perdew (LDA/BP). The obtained interaction energies differences at the equilibrium distance Re (C,Tl) range from 33 and 46 kJ/mol at the different levels used. These results indicate that the interaction between olefinic systems and Tl(I) are a real minimum on the potential energy surfaces (PES). We can predict that these new complexes are viable for synthesizing. At long distances, the behavior of the [C2Hn],Tl+ interaction may be related mainly to charge-induced dipole and dispersion terms, both involving the individual properties of the olefinic ,-system and thallium ion. However, the charge-induced dipole term (R,4) is found as the principal contribution in the stability at long and short distances. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 [source] Application of standard DFT theory for nonbonded interactions in soft matter: Prototype study of poly- para -phenyleneJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 2 2006Marcelo Alves-Santos Abstract We present a detailed analysis of the application of density functional theory (DFT) methods to the study of structural properties of molecular and supramolecular systems, using as a paradigmatic example three para -phenylene-based systems: isolated biphenyl, single chain poly- para -phenylene, and crystalline biphenyl. We use different functionals for the exchange correlation potential, the local density (LDA), and generalized gradient approximations (GGA), and also different basis sets expansions, localized, plane waves (PW), and mixed (localized plus PW), within the reciprocal space formulation for the hamiltonian. We find that regardless of the choice of basis functions, the GGA calculations yield larger interring distances and torsion angles than LDA. For the same XC approximation, the agreement between calculations with different basis functions lies within 1% (LDA) or 0.5% (GGA) for distances, and while PW and mixed basis calculations agree within 1° for torsion angles, the localized basis results show larger angles by , 8° and a nonmonotonic dependence on basis size, with differences within 6°. The most prominent features, namely the torsion between rings for isolated molecule and infinite chain, and planarity for the molecule in crystalline environment, are well reproduced by all DFT calculations. © 2005 Wiley Periodicals, Inc. J Comput Chem 27: 217,227, 2006 [source] Quasiparticle approximations and electron propagator theoryINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 4-5 2003J. V. Ortiz Abstract A comparison of quasiparticle concepts arising from the Dyson equation of electron propagator theory and from orbital functional theory shows close relationships between self,energy expressions in the former to correlation potentials in the latter. Detailed formulae are presented for second-order theories with general occupation numbers. Limitations of the Dyson and Landau quasiparticle concepts in the context of perturbative correlation formulae are discussed. Numerical results on N2, H2O, and their valence ionization energies are presented. Comparisons are made between total energy differences, orbital energies, and transition operator results. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003 [source] Time-dependent density functional theory for nonadiabatic processesISRAEL JOURNAL OF CHEMISTRY, Issue 1-2 2005Roi Baer Time-dependent density functional theory (TDDFT) is a general and robust method allowing the study of electron dynamics whether induced by nuclear motion or by external fields. We give a brief overview of the theory and some numerical methods together with recent applications stressing the generality and wide applicability of the method. We also discuss recent attempts to extend the present TDDFT by incorporating memory terms into the exchange correlation potentials. [source] Interaction of Cu+ and Cu2+ ions with ,-alanine.JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 8 2002A density functional study Abstract The Cu+ and Cu2+ preferred binding sites on ,-alanine and their affinity values for this amino acid were determined at the density functional level using three different hybrid exchange correlation potentials and the 6,311++G** basis set. The results demonstrated that the two ions both give stable complexes with ,-alanine but the stability order of the metalated species and the coordination sites are different depending on the nature of the cation. In particular, the Cu+,,-alanine ground-state structure is characterized by an ,2 -N,O coordination with the nitrogen and oxygen atoms belonging to the amino and carbonyl groups, respectively. In contrast, the most stable complex of the Cu2+,,-alanine system has an ,2 -O,O coordination with the cation bonded to the ,CO2, moiety of the zwitterionic form of the amino acid. Comparison with the Cu+ and Cu2+ affinity values for glycine, computed at the same levels of theory, demonstrated that the relative values do not change significantly as different hybrid functionals are used, although the absolute affinities are strongly influenced by the choice of the hybrid potential. Copyright © 2002 John Wiley & Sons, Ltd. [source] | ||||||||||