Search for dissertations about: "time-dependent exchange-correlation potential"

Found 4 swedish dissertations containing the words time-dependent exchange-correlation potential.

2. 1. Role of charge and spin fluctuations and their interplay in solids : A Green’s function approach

   Author : Tor Sjöstrand; Matematisk fysik; []
   Keywords : NATURVETENSKAP; NATURAL SCIENCES; Green’s function; correlations; collective excitations; screened interaction; electric polarization; orbital and spin magnetization; magnon-phonon interaction; Fierz ambiguity; time-dependent exchange-correlation potential;

   Abstract : Due to the large number of electrons, solid state physics boils down to many-body approximations in which only selected types of collective excitations are taken into account, guided by the emergent properties of the material under study. In this thesis, the collective excitations of primary interest are electronic charge and spin fluctuations(plasmons and magnons) and nuclear charge fluctuations (phonons). READ MORE

4. 2. Efficient Calculation of Nonlinear Spectroscopic Properties within the Time-Dependent Density Functional Theory Approximation

   Author : Karan Ahmadzadeh; Patrick Norman; Johannes Neugebauer; KTH; []
   Keywords : NATURVETENSKAP; NATURAL SCIENCES; Cubic response; DFT; Response theory; Theoretical Chemistry and Biology; Teoretisk kemi och biologi;

   Abstract : This thesis introduces a novel computational scheme tailored for efficient calculations of nonlinear spectroscopic observables. First, a derivation and implementation of an algorithm designed to harness the linearity of the Fock matrix construction in calculating two-photon absorption cross-sections within the self-consistent field approximation is presented. READ MORE

5. 3. Dynamics and Fluctuations in Single-Electron Tunneling Devices

   Author : Niklas Dittmann; Chalmers tekniska högskola; []
   Keywords : NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; quantum dot; time-dependent density-functional theory; perturbation theory; single-electron source;

   Abstract : In recent years, it has been routinely achieved to build nanoscale electronic devices, which generate current pulses carrying only a single elementary charge. Realizations of these single-electron emitters are based on time-dependently driven quantum dots, on single-electron turnstiles built from superconductor/normal-metal hybrid structures, and also on nanosystems employing Lorentzian voltage pulses or surface acoustic waves. READ MORE

6. 4. Model Vertices Beyond the GW Approximation

   Author : Mikael Hindgren; Matematisk fysik; []
   Keywords : NATURVETENSKAP; NATURAL SCIENCES; Matematisk och allmän teoretisk fysik; thermodynamics; statistical physics; gravitation; GW approximation; Electron self energy; Green s function; consistency; local-field corrections; vertex function; conserving approximations; variational energies; Mathematical and general theoretical physics; classical mechanics; relativity; quantum mechanics; klassisk mekanik; kvantmekanik; relativitet; statistisk fysik; termodynamik; Fysicumarkivet A:1997:Hindgren;

   Abstract : We study the effects of local vertex corrections to the self energy of the electron gas. We find that a vertex derived from time-dependent density-functional theory can give accurate self energies without including the explicit time dependence of the exchange-correlation potential provided, however, that a proper decay at large momentum transfer (large q) is built into the vertex function. READ MORE