X-Git-Url: https://hackdaworld.org/gitweb/?p=lectures%2Flatex.git;a=blobdiff_plain;f=posic%2Fthesis%2Fbasics.tex;h=8ab5002715fe796e75e78a2a78ad2c3b3db94976;hp=b1beb7f85c762f2cc72b36ae804f96c072285229;hb=7340b277821e2725d1f47f7d1cf230a7a1b0a943;hpb=6b8e82e926099b05e961285bb4307711d1aa8d3e diff --git a/posic/thesis/basics.tex b/posic/thesis/basics.tex index b1beb7f..8ab5002 100644 --- a/posic/thesis/basics.tex +++ b/posic/thesis/basics.tex @@ -277,18 +277,16 @@ It provides a stable algorithm that allows smooth changes of the system to new v \section{Denstiy functional theory} \label{section:dft} -In quantum-mechanical modeling the problem of describing a many-body problem is manifested in the high-dimensional Schr\"odinger equation for the wave function $\Psi({\vec{R}},{\vec{r}})$ that depends on the coordinates of the nuclei and electrons. +In quantum-mechanical modeling the problem of describing the many-body problem, i.e. a system of a large amount of interacting particles, is manifested in the high-dimensional Schr\"odinger equation for the wave function $\Psi({\vec{R}},{\vec{r}})$ that depends on the coordinates of all nuclei and electrons. The Schr\"odinger equation contains the kinetic energy of the ions and electrons as well as the electron-ion, ion-ion and electron-electron interaction. This cannot be solved exactly and there are several layers of approximations to reduce the number of parameters. -In density functional theory (DFT) the problem is recasted to the charge density $n(\vec{r})$ instead of using the description by a wave function. +The key point in density functional theory (DFT) is to recast the problem to a description using the charge density $n(\vec{r})$ that depends on only three spatial coordinates instead of the many-body wave function. Formally DFT can be regarded as an exactification of both, the Thomas Fermi and Hartree theory. - -Since {\textsc vasp} \cite{kresse96} is used in this work, theory and implementation of sophisticated algorithms of DFT codes is not subject of this work. -Thus, the content of the following sections is restricted to the very basic idea of DFT. +In the following sections the basic idea of DFT will be outlined. \subsection{Born-Oppenheimer approximation} -The first approximation ... +The first approximation employed \subsection{Hohenberg-Kohn theorem}