Search results for "Density Functional Theory."
showing 10 items of 935 documents
Continuity equation and local gauge invariance for the N3LO nuclear energy density functionals
2011
Background: The next-to-next-to-next-to-leading order (N3LO) nuclear energy density functional extends the standard Skyrme functional with new terms depending on higher-order derivatives of densities, introduced to gain better precision in the nuclear many-body calculations. A thorough study of the transformation properties of the functional with respect to different symmetries is required, as a step preliminary to the adjustment of the coupling constants. Purpose: Determine to which extent the presence of higher-order derivatives in the functional can be compatible with the continuity equation. In particular, to study the relations between the validity of the continuity equation and invari…
Nuclear energy density optimization: Shell structure
2013
Nuclear density functional theory is the only microscopical theory that can be applied throughout the entire nuclear landscape. Its key ingredient is the energy density functional. In this work, we propose a new parameterization UNEDF2 of the Skyrme energy density functional. The functional optimization is carried out using the POUNDerS optimization algorithm within the framework of the Skyrme Hartree-Fock-Bogoliubov theory. Compared to the previous parameterization UNEDF1, restrictions on the tensor term of the energy density have been lifted, yielding a very general form of the energy density functional up to second order in derivatives of the one-body density matrix. In order to impose c…
Dipole surface plasmon in large K N + clusters
1993
The dipole surface plasmon forK N + clusters is analyzed using the RPA sum-rule technique within a semiclassical Density Functional Theory and the spherical jellium model. The theoretical frequencies are blue shifted as compared to the experimental ones. The discrepancies between theory and experiment are reduced when considering non-local energy contributions in the density functional and phenomenologically including atomic lattice effects by means of an electron effective mass and a static dielectric constant.
Sum Frequency Generation Spectra from Velocity-Velocity Correlation Functions: New Developments and Applications
2018
At the interface, the properties of water can be rather different from those observed in the bulk. In this chapter we present an overview of our computational approach to understand water structure and dynamics at the interface including atomistic and electronic structure details. In particular we show how Density Functional Theory-based molecular dynamics simulations (DFT-MD) of water interfaces can provide a microscopic interpretation of recent experimental results from surface sensitive vibrational Sum Frequency Generation spectroscopy (SFG). In our recent work we developed an expression for the calculation of the SFG spectra of water interfaces which is based on the projection of the at…
Two-component density-functional theory: Application to positron states.
1985
A quantitative approach to calculating properties of inhomogeneous two-component Coulomb-Fermi systems is presented. As an application, the ground-state electronic structure of a jellium vacancy containing a trapped positron is calculated self-consistently. While the resulting density profiles and energetics are quite different from those obtained neglecting cross correlations, the conventional estimates for the annihilation rates are shown to remain valid, due to canceling effects of the increase in the mean electron density and the decrease in short-range screening.
Local correlation functional for electrons in two dimensions
2008
We derive a local approximation for the correlation energy in two-dimensional electronic systems. In the derivation we follow the scheme originally developed by Colle and Salvetti for three dimensions, and consider a Gaussian approximation for the pair density. Then, we introduce an ad-hoc modification which better accounts for both the long-range correlation, and the kinetic-energy contribution to the correlation energy. The resulting functional is local, and depends parametrically on the number of electrons in the system. We apply this functional to the homogeneous electron gas and to a set of two-dimensional quantum dots covering a wide range of electron densities and thus various amount…
Colle-Salvetti-type local density functional for the exchange-correlation energy in two dimensions
2010
We derive an approximate local density functional for the exchange-correlation energy to be used in density-functional calculations of two-dimensional systems. In the derivation we employ the Colle-Salvetti wave function within the scheme of Salvetti and Montagnani [Phys. Rev. A 63, 052109 (2001)] to satisfy the sum rule for the exchange-correlation hole. We apply the functional for the two-dimensional homogeneous electron gas as well as to a set of quantum dots and find a very good agreement with exact reference data.
Quantum dots in magnetic fields: Unrestricted symmetries in the current spin-density functional formalism
1999
We apply the current spin-density functional formalism (CSDFT) of Vignale and Rasolt to two-dimensional quantum dots in magnetic fields. Avoiding any spatial symmetry restrictions of the solutions, we find that a broken rotational symmetry of the electronic charge density can occur in high magnetic fields.
Time-resolved photoabsorption in finite systems: A first-principles NEGF approach
2016
We describe a first-principles NonEquilibrium Green’s Function (NEGF) approach to time-resolved photoabsortion spectroscopy in atomic and nanoscale systems. The method is used to highlight a recently discovered dynamical correlation effect in the spectrum of a Krypton gas subject to a strong ionizing pump pulse. We propose a minimal model that captures the effect, and study the performance of time-local approximations versus time-nonlocal ones. In particular we implement the time-local Hartree-Fock and Markovian second Born (2B) approximation as well as the exact adiabatic approximation within the Time-Dependent Density Functional Theory framework. For the time-nonlocal approximation we ins…
Symmetry and Electronic Structure of Noble Metal Nanoparticles and the Role of Relativity
2004
High resolution photoelectron spectra of cold mass selected Cu_n-, Ag_n- and Au_n- with n =53-58 have been measured at a photon energy of 6.42 eV. The observed electron density of states is not the expected simple electron shell structure, but seems to be strongly influenced by electron-lattice interactions. Only Cu55- and Ag55- exhibit highly degenerate states. This is a direct consequence of their icosahedral symmetry, as is confirmed by density functional theory calculations. Neighboring sizes exhibit perturbed electronic structures, as they are formed by removal or addition of atoms to the icosahedron and therefore have lower symmetries. Gold clusters in the same size range show complet…