Tf. Fassler et al., VISUALIZATION OF TIGHT-BINDING CALCULATIONS - THE ELECTRONIC-STRUCTURE AND ELECTRON LOCALIZATION OF THE SI(100) SURFACE, Chemistry, 1(9), 1995, pp. 625-633
The advantage of computer graphics in the visualization of tight-bindi
ng calculations is highlighted in a model study of the reconstruction
of the Si(100) surface. Three different surface models-the unreconstru
cted surface Si(100)-(1 x 1), and symmetric and asymmetric pairing of
surface atoms Si(100)-(2 x 1)-are investigated on the basis of density
of states (DOS), local (projected) density of stales (LDOS) and cryst
al orbital-overlap population (COOP) analysis. For the visualization o
f the real-space properties of tight-binding calculations, two- and th
ree-dimensional images of the total (TED) and partial electron densiti
es (PED) are shown. The PED calculated near the Fermi level are compar
ed to densities of HOMOs and LUMOs in molecular systems and used to an
alyse constant current mode STM images, obtained by applying bias volt
ages of different sign. They shaw excellent agreement with STM experim
ents. The electron-localization function (ELF) has been shown to descr
ibe chemical bonds in molecules and solids surprisingly well. Here, th
e ELF is calculated for surfaces. In order to visualize the shape of t
he ''dangling'' surface bonds and bonds connecting surface atoms, two-
and three-dimensional representations of the ELF are discussed. Using
the reconstruction of the Si(100) surface as an example, we show that
combining methods for extracting information from quantum mechanical
calculations, such as PED, TED and ELF, leads to a more comprehensive
description of the electronic surface structure. With the help of comp
uter graphics, chemical concepts routinely used for describing local p
roperties of molecules can be transferred very effectively to extended
systems.