Measuring Density Functional Parameters from Electron Diffraction Patterns

TL;DR

This paper introduces QCBED-DFT, a method combining electron diffraction and density functional theory to accurately measure electronic parameters and atomic positions in complex materials.

Contribution

It presents a novel approach integrating DFT with electron diffraction to directly refine model parameters from experimental data.

Findings

Measured Hubbard U for NiO and CeB6 with high precision.

Determined boron positional parameter in CeB6 accurately.

Provided an accuracy test for electron density models.

Abstract

We have integrated density functional theory (DFT) into quantitative convergent-beam electron diffraction (QCBED) to create a synergy between experiment and theory called QCBED-DFT. This synergy resides entirely in the electron density which, in real materials, gives rise to the experimental CBED patterns used by QCBED-DFT to refine DFT model parameters. We used it to measure the Hubbard energy, U, for two strongly correlated electron systems, NiO and CeB6 (UNiO = 7.4 +/- 0.6 eV and UCeB6 = 3.0 +/- 0.6 eV), and the boron position parameter, x, for CeB6 (x = 0.1992 +/- 0.0003). In verifying our measurements, we demonstrate an accuracy test for any modelled electron density.