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Many-body Effects (many-body + effects)
Selected AbstractsMany-body effects on structure and dynamics of aqueous ionic solutionsJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 10 2003Hannes H. Loeffler Abstract We performed several molecular dynamic studies of metal cations in aqueous solution. The alkali metal ion Li+ and the first-row transition metal ion Mn2+ have been chosen as model systems. Two different three-body corrections are proposed to mimic the crucial many-body effects of electrolyte solutions. The correction function, which includes attractive features of the three-body potential, performs considerably better than the purely repulsive interaction function. Structural and dynamic results show that this simple enhancement is able to satisfactorily reproduce experimental and higher-level results for the first hydration shell. © 2003 Wiley Periodicals, Inc. J Comput Chem 24: 1232,1239, 2003 [source] Ab-initio simulations of materials using VASP: Density-functional theory and beyondJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 13 2008Jürgen Hafner Abstract During the past decade, computer simulations based on a quantum-mechanical description of the interactions between electrons and between electrons and atomic nuclei have developed an increasingly important impact on solid-state physics and chemistry and on materials science,promoting not only a deeper understanding, but also the possibility to contribute significantly to materials design for future technologies. This development is based on two important columns: (i) The improved description of electronic many-body effects within density-functional theory (DFT) and the upcoming post-DFT methods. (ii) The implementation of the new functionals and many-body techniques within highly efficient, stable, and versatile computer codes, which allow to exploit the potential of modern computer architectures. In this review, I discuss the implementation of various DFT functionals [local-density approximation (LDA), generalized gradient approximation (GGA), meta-GGA, hybrid functional mixing DFT, and exact (Hartree-Fock) exchange] and post-DFT approaches [DFT + U for strong electronic correlations in narrow bands, many-body perturbation theory (GW) for quasiparticle spectra, dynamical correlation effects via the adiabatic-connection fluctuation-dissipation theorem (AC-FDT)] in the Vienna ab initio simulation package VASP. VASP is a plane-wave all-electron code using the projector-augmented wave method to describe the electron-core interaction. The code uses fast iterative techniques for the diagonalization of the DFT Hamiltonian and allows to perform total-energy calculations and structural optimizations for systems with thousands of atoms and ab initio molecular dynamics simulations for ensembles with a few hundred atoms extending over several tens of ps. Applications in many different areas (structure and phase stability, mechanical and dynamical properties, liquids, glasses and quasicrystals, magnetism and magnetic nanostructures, semiconductors and insulators, surfaces, interfaces and thin films, chemical reactions, and catalysis) are reviewed. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2008 [source] Many-body effects on structure and dynamics of aqueous ionic solutionsJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 10 2003Hannes H. Loeffler Abstract We performed several molecular dynamic studies of metal cations in aqueous solution. The alkali metal ion Li+ and the first-row transition metal ion Mn2+ have been chosen as model systems. Two different three-body corrections are proposed to mimic the crucial many-body effects of electrolyte solutions. The correction function, which includes attractive features of the three-body potential, performs considerably better than the purely repulsive interaction function. Structural and dynamic results show that this simple enhancement is able to satisfactorily reproduce experimental and higher-level results for the first hydration shell. © 2003 Wiley Periodicals, Inc. J Comput Chem 24: 1232,1239, 2003 [source] Determination of carrier diffusion coefficient and lifetime in single crystalline CVD diamonds by light-induced transient grating techniquePHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 9 2010T. Malinauskas Abstract We report on a contactless, all-optical study of carrier diffusion and recombination kinetics in single-crystalline diamond layers using the light-induced transient grating (LITG) technique. Decay times of transient diffraction grating yielded carrier lifetime of ,R,,,3,ns and bipolar diffusion coefficient Da,=,12,cm2/s at 300,K. The latter value of Da was found to be 4,5 times lower than the ambipolar diffusivity based on electron and hole mobilities, measured by photo-electrical time-of-flight (ToF) technique. This discrepancy was attributed to the bandgap renormalization at high excess carrier densities and its impact on carrier diffusion. The significant decrease of low temperature diffusivity pointed out to a contribution of many-body effects which are tentatively attributed to the formation of electron,hole liquid (EHL) at T,<,150,K. [source] First principles approach to binding energies of excitons, trions and biexcitons in quantum wellsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2003A. V. Filinov Abstract We present first-principle path integral Monte-Carlo (PIMC) studies of strongly correlated electron,hole complexes such as excitons, trions (charged excitons) and biexcitons in AlxGa1,xAs quantum-well structures. The correlation and binding energies are calculated as function of quantum well width L, for 10 Å , L , 250 Å and compared with available experimental [1] and theoretical [2,4] data. As in the experiments, we observe a maximum of the binding energies in GaAs/AlGaAs quantum well samples around L = 40 Å the physical reason of which is the non-monotonic dependence of the electron (hole) confinement on the well width. The developed method is a powerful tool for further systematic investigation of the influence of temperature and many-body effects on bound states in heterostructures (e.g. depedence on finite exciton, biexciton densities) and disorder (e.g. well-width fluctuations). [source] | ||||||||||