Surface Reconstructions and Bonding via the Electron Localization Function: The Case of Si(001)

TL;DR

This paper demonstrates that the electron localization function (ELF) offers detailed insights into surface reconstructions and bonding mechanisms in Si(001), revealing changes from metallic to covalent character upon reconstruction.

Contribution

It introduces the application of ELF within a first-principles framework to analyze surface bonding and reconstruction in covalent semiconductors.

Findings

Unreconstructed surface shows partly metallic character.

Reconstruction restores covalent bonding with strong electron pairing.

ELF visualizes bonding changes clearly.

Abstract

The bonding pattern of a covalent semiconductor is disrupted when a surface is cut while keeping a rigid (truncated bulk) geometry. The covalent bonds are partly reformed (with a sizeable energy gain) when reconstruction is allowed. We show that the ``electron localization function'' (ELF)---applied within a first--principles pseudopotential framework---provides un unprecedented insight into the bonding mechanisms. In the unreconstructed surface one detects a partly metallic character, which disappears upon reconstruction. In the surface reformed bonds, the ELF sharply visualizes strongly paired electrons, similar in character to those of the bulk bonds.