Metal impurities in an oxide: Ab initiostudy of electronic and structural properties of Cd in rutileTiO2

Leonardo A Errico,Gabriel Fabricius,Mario Rentería

doi:10.1103/physrevb.67.144104

Leonardo A Errico, Gabriel Fabricius + Show 1 more

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https://doi.org/10.1103/physrevb.67.144104

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Abstract

In this work we undertake the problem of a transition metal impurity in an oxide. We present an ab initio study of the relaxations introduced in ${\mathrm{TiO}}_{2}$ when a Cd impurity substitutionally replaces a Ti atom. Using the full-potential linearized-augmented-plane-wave method, we obtain relaxed structures for different charge states of the impurity and computed the electric-field gradients (EFGs) at the Cd site. We find that EFGs, and also relaxations, are dependent on the charge state of the impurity. This dependence is very remarkable in the case of the EFG and is explained by analyzing the electronic structure of the studied system. We predict fairly anisotropic relaxations for the nearest oxygen neighbors of the Cd impurity. The experimental confirmation of this prediction and a brief report of these calculations have recently been presented [Phys. Rev. Lett. 89, 55503 (2002)]. Our results for relaxations and EFGs are in clear contradiction with previous studies of this system that assumed isotropic relaxations, and point out that no simple model is viable to describe relaxations and the EFG at Cd in ${\mathrm{TiO}}_{2}$ even approximately.

Highlights

The problem of metal impurities in oxides is a challenge in solid-state physics both from fundamental and applied points of view
In that work we performed a FLAPW calculation of the relaxations introduced by the impurity, and studied their interplay with the electronic structure of the system, predicting highly anisotropic relaxations of the nearest neighbors of the impurity and a drastic change in the orientation of the principal component of the EFG tensor
In this work we have studied, through a series of firstprinciples calculations, the problem of a Cd impurity substitutionally-located at the cationic site in rutile TiO2

Summary

Introduction

The problem of metal impurities in oxides is a challenge in solid-state physics both from fundamental and applied points of view. In an oxide (TiO2) was recently reported.[16] In that work we performed a FLAPW calculation of the relaxations introduced by the impurity, and studied their interplay with the electronic structure of the system, predicting highly anisotropic relaxations of the nearest neighbors of the impurity and a drastic change in the orientation of the principal component of the EFG tensor. This prediction was confirmed in the same work by a key TDPAC experiment. We discuss in detail the precision of our calculations, studying its dependence on the different parameters that control the precision ~impurity dilution, base dimension, average in k space, etc.! and its dependence on the approximation used for the exchange-correlation potential

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