Sökning: "Density functional perturbation theory"

Visar resultat 1 - 5 av 20 avhandlingar innehållade orden Density functional perturbation theory.

1. 1. Ab initio Lattice Dynamics : Hydrogen-dense and Other Materials

   Författare :Duck Young Kim; Rajeev Ahuja; Richard Needs; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Density functional theory; Density functional perturbation theory; Hydrogen-dense materials; Phase transition; High pressure; Ab initio lattice dynamics; Superconductivity; Quasi-particle approximation; Physics; Fysik;

   Sammanfattning : This thesis presents a theoretical study of materials under high pressure using ab initio lattice dynamics based on density functional theory and density functional perturbation theory using both super-cell and linear response approach. Ab initio lattice dynamics using super-cell approach is applied to compare our theoretical predictions with experimental findings. LÄS MER

3. 2. Some Aspects of Non-Perturbative Quantum Field Theory

   Författare :Joakim Hallin; Chalmers tekniska högskola; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Yang-Mills; QED; pair production; density matrix; external field; Schwinger model; gauge invariant; functional representation;

   Sammanfattning : The aim of this thesis is to describe some different ways in which non-perturbative methods enter in quantum field theory. In the thesis such methods enter in 1+1-dimensional theories: various Yang-Mills theories and electrodynamics. It also enters when treating charged bosons or fermions interacting with an external, classical field. LÄS MER

4. 3. Time-Dependent Many-Body Perturbation Theory: Possibilities and Limitations

   Författare :Marc Puig von Friesen; Matematisk fysik; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Many-body perturbation theory; Correlation functions; Hubbard model; Non-equilibrium Green s functions; Fysicumarkivet A:2011:Puig von Friesen;

   Sammanfattning : This dissertation investigates the possibilities and limitations of time-dependent many-body perturbation theory by studying small Hubbard clusters for which the exact solution is available. The first part of the thesis is comprised of a short introduction to the concepts and methodologies used. LÄS MER

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

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

   Sammanfattning : 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. LÄS MER

7. 5. Application and development of quantum chemical methods. Density functional theory and valence bond theory

   Författare :Fuming Ying; Olav Vahtras; KTH; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Theoretical chemistry; Teoretisk kemi;

   Sammanfattning : This thesis deals with two disjoint subdiciplines of quantum chemistry.  One isthe most used electronic structure method today, density functional theory(DFT), and the other one of the least used electronic structure methods,valence bond theory (VB). LÄS MER