Dimitri Van Neck

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Standard normal mode analysis becomes problematic for complex molecular systems, as a result of both the high computational cost and the excessive amount of information when the full Hessian matrix is used. Several partial Hessian methods have been proposed in the literature, yielding approximate normal modes. These methods aim at reducing the computational(More)
The similarities between Hartree-Fock (HF) theory and the density matrix renormalization group (DMRG) are explored. Both methods can be formulated as the variational optimization of a wave-function Ansatz. Linearization of the time-dependent variational principle near a variational minimum allows to derive the random phase approximation (RPA). We show that(More)
The density matrix renormalization group (DMRG) has become an indispensable numerical tool to find exact eigenstates of finitesize quantum systems with strong correlation. In the fields of condensed matter, nuclear structure and molecular electronic structure, it has significantly extended the system sizes that can be handled compared to full configuration(More)
We consider low-dimensional model systems with a fixed two-body interaction and a variable ~nonlocal! one-body potential. It is shown explicitly that an extended domain of allowed ~N-representable! one-body density matrices cannot be generated in this way, the excluded domain depending on the two-body interaction under consideration. This stands in contrast(More)
Normal mode analysis (NMA) is a well-known technique which estimates the intrinsic frequencies of chemical systems by assuming a harmonic shape for the potential energy surface. Despite its simplicity, it is still a popular approach to predict vibrational IR and Raman spectra, to identify chemical groups [1], or to study the large motions involved in(More)
Until recently, normal mode analysis (NMA) was limited to small proteins, not only because the required energy minimization is a computationally exhausting task, but also because NMA requires the expensive diagonalization of a 3Na×3Na matrix with Na the number of atoms. A series of simplified models has been proposed, in particular the RotationTranslation(More)
The strong short-range and tensor components of the nucleon–nucleon interactions induce correlations in the nuclear wave function which are going beyond the independent–particle approximation, e.g., the Hartree–Fock method. Therefore it has always been a point of experimental and theoretical interest to find observables, which reflect these correlations in(More)
Present applications of the dispersive-optical-model analysis are restricted by the use of a local but energydependent version of the generalized Hartree-Fock potential. This restriction is lifted by the introduction of a corresponding nonlocal potential without explicit energy dependence. Such a strategy allows for a complete determination of the nucleon(More)
We propose a framework to construct the ground-state energy and density matrix of an N-electron system by solving selfconsistently a set of single-particle equations. The method can be viewed as a non-trivial extension of the Kohn-Sham scheme (which is embedded as a special case). It is based on separating the Green’s function into a quasi-particle part and(More)