Simulation of electron energy loss spectra of nanomaterials with linear-scaling density functional theory

E W Tait,L E Ratcliff,M C Payne,P D Haynes,N D M Hine

doi:10.1088/0953-8984/28/19/195202

Abstract

Experimental techniques for electron energy loss spectroscopy (EELS) combine high energy resolution with high spatial resolution. They are therefore powerful tools for investigating the local electronic structure of complex systems such as nanostructures, interfaces and even individual defects. Interpretation of experimental electron energy loss spectra is often challenging and can require theoretical modelling of candidate structures, which themselves may be large and complex, beyond the capabilities of traditional cubic-scaling density functional theory. In this work, we present functionality to compute electron energy loss spectra within the onetep linear-scaling density functional theory code. We first demonstrate that simulated spectra agree with those computed using conventional plane wave pseudopotential methods to a high degree of precision. The ability of onetep to tackle large problems is then exploited to investigate convergence of spectra with respect to supercell size. Finally, we apply the novel functionality to a study of the electron energy loss spectra of defects on the (1 0 1) surface of an anatase slab and determine concentrations of defects which might be experimentally detectable.

Highlights

Continual improvements in microscope technology in recent years have greatly increased the utility of electron energy loss spectroscopy (EELS) in the characterization of materials
Greater information about the local structure and chemistry is encoded in the energy loss near edge structure (ELNES), but interpretation of this is hampered by a lack of simple methods to extract this information from spectra
We have demonstrated an efficient method for the computa tion of electron energy loss spectra for large, complex nano materials systems

Summary

Introduction

Continual improvements in microscope technology in recent years have greatly increased the utility of electron energy loss spectroscopy (EELS) in the characterization of materials. Signatures from surfaces may be extracted [6]. Greater information about the local structure and chemistry is encoded in the energy loss near edge structure (ELNES), but interpretation of this is hampered by a lack of simple methods to extract this information from spectra. Theoretical spectr oscopy can be invaluable in such cases as it provides a means to compute spectra for proposed model structures, from which the best match to experiment can be found [7]

Objectives

Methods

Conclusion