A new table-direct CI (TDCI) scheme based on the table CI method for the direct computation of Hamiltonian matrix elements whose basis functions are linear combinations of spin-adapted functions ψα is presented, in which the explicit calculation and storage of the Hamiltonian matrix H in the basis {ψα} is avoided. Two algorithms are provided for the matrix element evaluation; (i) within the iterative Davidson diagonalization procedure of H and (ii) within the individualized configuration selection scheme of Buenker and Peyerimhoff, as included in the MRD-CI program of these authors. The new algorithm is employed to compute the equilibrium structural parameters of the lowest X 2A1 and A 2B2 states of NO2, solving secular equations of dimension 190 000 spin-adapted functions (384 000 determinants, 32 000 configurations), as well as the Te value for the corresponding transition.

Please cite this article as: T. Lostak, S. Krebs, A. Maljusch, T. Gothe, M. Giza, M. Kimpel, J. Flock, S. Schulz, Formation and characterization of Fe 3+ -/Cu 2+ -modified zirconium oxide conversion layers on zinc alloy coated steel sheets, Electrochimica Acta (2013), http://dx. AbstractZirconium oxide conversion layers are considered as environmentally friendly alternatives replacing chromate-based passivation layers in the coil-coating industry. Based on excellent electronic barrier properties they provide an effective corrosion protection of the metallic substrate. In this work, thin layers were grown on HDG-steel-substrates by increasing the local pH at the surface and were characterized using potentiodynamic polarization technique.The influence of Cu(NO 3 ) 2 3H 2 O or Fe(NO 3 ) 3 9H 2 O on morphology and thickness of deposited protective layers were investigated by XPS, ToF-SIMS and FE-SEM. A significant film thickness increase was found by adding Cu 2+ or Fe 3+ ions to the conversion solution. In addition, growth kinetics were studied by in-situ measurements of corrosion potential using potentiodynamic polarization technique.

Zr-based conversion layers are considered as environmentally friendly alternatives replacing trication phosphatation in the automotive industry. Based on excellent electronic barrier properties they provide an effective corrosion protection of the metallic substrate. In this work, thin protective layers were grown on novel Zn-Al-Mg alloy coated steel sheets by increasing the local pH-value at the sample surface leading to deposition of a Zr-based conversion layer. For this purpose Zn-Al-Mg alloy (ZM) coated steel sheets were treated in an aqueous model conversion solution containing well-defined amounts of hexafluorozirconic acid (H2ZrF6) and characterized after different immersion times with SKPFM and field emission SEM (FE-SEM)/EDX techniques. A deposition mechanism of Zr-based conversion coatings on microstructural heterogeneous Zn-Al-Mg alloy surfaces was proposed.

The spatial extension of the C2H4 (π,π*)1V state is investigated by means of low selection threshold multireference configuration interaction (CI) calculations employing two atomic orbital (AO) basis sets with different numbers of polarization and Rydberg functions. The results are shown to be nearly independent of the choice of one-electron basis (ground N, triplet T, and singlet V self-consistent field molecular orbitals (SCF MOs)) in forming the many-electron basis for the configuration interaction indicating that the AO basis limit has been closely approached in each case. The calculations indicate that the value for the 〈ΨV|Σxi2|ΨV〉≡〈x2〉V matrix element falls in the 18±1 a02 range, 50% larger than the corresponding values computed for 〈x2〉N and 〈x2〉T, respectively, for the corresponding N and T states. This result is interpreted to be a consequence of the mixing of diabatic (π,π*)1 valence and (πd,π)1 Rydberg states in the Franck–Condon region of the V–N transition. The corresponding excitation energy is computed to lie in the 7.90–7.95 eV range, indicating that there is a distinct nonverticality in the measured absorption spectrum which is caused in part by nonadiabatic interactions between the V and (π,3py)1 Rydberg states as a result of torsional motion of the C2H4 molecule.

The rationale for carrying out multireference single-and double-excitation config uration interaction (CI) calculations to obtain highly correlated electronic wavefunctions for atoms and molecules is discussed. A detailed description of com putational algorithms for implementing a configuration-driven approach for this type of theoretical treatment is given, with emphasis on the use of CI tables to enable an efficient evaluation of Hamiltonian matrix elements between Slater de terminants spanning configurations with many open shells. These techniques have recently been incorporated in a Table-Direct CI program version (TD-CI) which minimizes I/O operations and thereby greatly expands the range of applicability of the configuration-driven approach. With the use of improved methods for recog nition of excitation relationships between configurations it has become possible in the current implementation to solve secular equations of order exceeding one million randomly selected linear combinations of Slater determinants which are eigenfunctions of the S 2 operator. Finally, timing results are presented for a num ber of test examples and a survey of possible future extensions of these methods is undertaken. IntroductionExperience with electronic structure calculations for atoms and molecules has underscored the need to go beyond the Hartree-Fock limit and provide for an accurate treatment of electron correlation effects on a widely applicable basis. The single-determinant wave function of the self-consistent-field (SCF) methodology is unable to describe dissociation processes in a satisfactory man ner except in rare cases, and it is also quite unreliable for the prediction of en ergy differences between electronic states possessing different numbers of open shells. The configuration interaction (CI) method is a straightforward means of introducing correlation in the electronic wave function, but the scope of the computations becomes overwhelming if carried to its logical conclusion (full CI) for a suitably flexible atomic orbital (AO) basis. This state of affairs has led to a search for ways to restrict the CI space to only the most important electronic configurations while still retaining a high degree of reliability for the Recent Advances in Multireference Methods Downloaded from www.worldscientific.com by NANYANG TECHNOLOGICAL UNIVERSITY on 10/01/15. For personal use only.

One of the major challenges of voltage stabilization in converter-based DC microgrids are the multiple interacting units displaying intermittent supply behavior. In this paper, we address this by a decentralized scalable, plug-and-play voltage controller for voltage-source converters (VSCs) at primary level. In contrast to existing approaches, we follow a systematic and constructive design based on port-Hamiltonian systems (PHSs) which does neither require the heuristic proposition of a Lyapunov function nor the computation of auxilliary variables such as time-derivatives. By employing the Hamiltonian naturally obtained from the PHS approach as Lyapunov function and using the modularity of passive systems, we provide sufficient conditions under which the designed VSC controllers achieve microgrid-wide asymptotic voltage stability. Integral action (IA), which preserves the passive PHS structure, robustifies the design against unknown disturbances and ensures zero voltage errors in the steady-state. Numerical simulations illustrate the functionality of the proposed voltage controller. arXiv:2002.05050v1 [eess.SY]

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