Search results for "Configuration"
showing 10 items of 601 documents
High-precision ab initio calculations of the spectrum of Lr$^+$
2019
The planned measurement of optical resonances in singly-ionised lawrencium (Z = 103) requires accurate theoretical predictions to narrow the search window. We present high-precision, ab initio calculations of the electronic spectra of Lr$^+$ and its lighter homologue lutetium (Z = 71). We have employed the state-of-the-art relativistic Fock space coupled cluster approach and the AMBiT CI+MBPT code to calculate atomic energy levels, g-factors, and transition amplitudes and branching-ratios. Our calculations are in close agreement with experimentally measured energy levels and transition strengths for the homologue Lu$^+$ , and are well-converged for Lr$^+$ , where we expect a similar level o…
Regular packings on periodic lattices.
2011
We investigate the problem of packing identical hard objects on regular lattices in d dimensions. Restricting configuration space to parallel alignment of the objects, we study the densest packing at a given aspect ratio X. For rectangles and ellipses on the square lattice as well as for biaxial ellipsoids on a simple cubic lattice, we calculate the maximum packing fraction \phi_d(X). It is proved to be continuous with an infinite number of singular points X^{\rm min}_\nu, X^{\rm max}_\nu, \nu=0, \pm 1, \pm 2,... In two dimensions, all maxima have the same height, whereas there is a unique global maximum for the case of ellipsoids. The form of \phi_d(X) is discussed in the context of geomet…
Thermodynamics based on the principle of least abbreviated action: Entropy production in a network of coupled oscillators
2006
We present some novel thermodynamic ideas based on the Maupertuis principle. By considering Hamiltonians written in terms of appropriate action-angle variables we show that thermal states can be characterized by the action variables and by their evolution in time when the system is nonintegrable. We propose dynamical definitions for the equilibrium temperature and entropy as well as an expression for the nonequilibrium entropy valid for isolated systems with many degrees of freedom. This entropy is shown to increase in the relaxation to equilibrium of macroscopic systems with short-range interactions, which constitutes a dynamical justification of the Second Law of Thermodynamics. Several e…
Inherent structure entropy of supercooled liquids
1999
We present a quantitative description of the thermodynamics in a supercooled binary Lennard Jones liquid via the evaluation of the degeneracy of the inherent structures, i.e. of the number of potential energy basins in configuration space. We find that for supercooled states, the contribution of the inherent structures to the free energy of the liquid almost completely decouples from the vibrational contribution. An important byproduct of the presented analysis is the determination of the Kauzmann temperature for the studied system. The resulting quantitative picture of the thermodynamics of the inherent structures offers new suggestions for the description of equilibrium and out-of-equilib…
Impact of New Physics on CP-Asymmetries at Long Baselines
2018
We study the impact of new physics on CP-asymmetries using different oscillation channels at long baseline experiments.
Exact solution of the 1D Hubbard model with NN and NNN interactions in the narrow-band limit
2013
We present the exact solution, obtained by means of the Transfer Matrix (TM) method, of the 1D Hubbard model with nearest-neighbor (NN) and next-nearest-neighbor (NNN) Coulomb interactions in the atomic limit (t=0). The competition among the interactions ($U$, $V_1$, and $V_2$) generates a plethora of T=0 phases in the whole range of fillings. $U$, $V_1$, and $V_2$ are the intensities of the local, NN and NNN interactions, respectively. We report the T=0 phase diagram, in which the phases are classified according to the behavior of the principal correlation functions, and reconstruct a representative electronic configuration for each phase. In order to do that, we make an analytic limit $T\…
First-principles electronic structure of spinelLiCr2O4:A possible half-metal
2004
We have employed first-principles electronic structure calculations to examine the hypothetical (but plausible) oxide spinel, ${\mathrm{LiCr}}_{2}{\mathrm{O}}_{4}$ with the ${d}^{2.5}$ electronic configuration. The cell (cubic) and internal (oxygen position) structural parameters have been obtained for this compound through structural relaxation in the first-principles framework. Within the one-electron band picture, we find that ${\mathrm{LiCr}}_{2}{\mathrm{O}}_{4}$ is magnetic, and a candidate half-metal. The electronic structure is substantially different from the closely related and well-known rutile half-metal ${\mathrm{CrO}}_{2}.$ In particular, we find a smaller conduction-band width…
Classical Geometric Phases: Foucault and Euler
2020
In the last chapter we saw how a quantum system can give rise to a Berry phase, by studying the adiabatic round trip of its quantum state on a certain parameter space. Rather than considering what happens to states in Hilbert space, we now turn to classical mechanics, where we are concerned instead with the evolution of the system in configuration space. As a first example, we are interested in the geometric phase of an oscillator that is constrained to a plane that is transported over some surface which moves along a certain path in three-dimensional space. Contrary to determining the Berry phase, there is no adiabatic approximation of the motion along the curve involved. The Foucault phas…
Spin Crossover, Liesst, and Niesst-Fascinating Electronic Games in Iron Complexes
1997
Abstract Coordination compounds of transition metal ions with open-shell electron configurations may exhibit dynamic electronic structure phenomena depending on the nature of the coordinating ligand sphere. The change of spin state with temperature (thermal spin crossover”) and light-induced electron transfer processes leading to long-lived metastable states are among the most fascinating electronic games encountered in transition metal compounds and are presently under intensive study by chemists and physicists. The first part of this lecture will survey briefly some highlights of previous work and present recent results on thermal spin crossover in iron(II) compounds. The second part of t…
Metal valence states inEu0.7NbO3,EuNbO3,andEu2Nb5O9by TB-LMTO-ASA band-structure calculations and resonant photoemission spectroscopy
1998
The electronic structures of ${\mathrm{Eu}}_{2}{\mathrm{Nb}}_{5}{\mathrm{O}}_{9},$ ${\mathrm{EuNbO}}_{3},$ and ${\mathrm{Eu}}_{0.7}{\mathrm{NbO}}_{3}$ have been investigated by photoemission and total-yield spectroscopy with synchrotron radiation, and in the case of ${\mathrm{Eu}}_{2}{\mathrm{Nb}}_{5}{\mathrm{O}}_{9}$ by tight-binding linear muffin-tin orbital (LMTO) band-structure calculations. A central question for reduced europium niobates is that of the valence of Eu and Nb. Both europium and niobium atoms can appear in different valence states so that various electronic configurations in the title compounds are possible. For this reason, the valence band was studied by the resonant Eu…