Electronic Structure of Dangling Bonds in Amorphous Silicon Studied via a Density-Matrix Functional Method

TL;DR

This study investigates the electronic properties of dangling bonds in hydrogenated amorphous silicon using a density-matrix functional approach, revealing charge localization, energy level splittings, and spin fluctuations consistent with experimental data.

Contribution

It introduces a density-matrix correlation-energy functional applied to a generalized Anderson Hamiltonian for analyzing dangling bonds in amorphous silicon, providing new insights into electron interactions.

Findings

Energy level splittings approach an asymptotic value for large U.

Electron spin is highly localized on the dangling bond.

Results align with experimental data and differ from Hartree-Fock predictions.

Abstract

A structural model of hydrogenated amorphous silicon containing an isolated dangling bond is used to investigate the effects of electron interactions on the electronic level splittings, localization of charge and spin, and fluctuations in charge and spin. These properties are calculated with a recently developed density-matrix correlation-energy functional applied to a generalized Anderson Hamiltonian, consisting of tight-binding one-electron terms parametrizing hydrogenated amorphous silicon plus a local interaction term. The energy level splittings approach an asymptotic value for large values of the electron-interaction parameter U, and for physically relevant values of U are in the range 0.3-0.5 eV. The electron spin is highly localized on the central orbital of the dangling bond while the charge is spread over a larger region surrounding the dangling bond site. These results are consistent with known experimental data and previous density-functional calculations. The spin fluctuations are quite different from those obtained with unrestricted Hartree-Fock theory.