SNIC SUPR
First principle calculations of paramagnetic NMR shifts and quadrupolar interaction parameters of deuterium in perovskite oxyhydrides.
Dnr:

SNIC 2019/5-64

Type:

SNIC Small Compute

Principal Investigator:

Rihards Aleksis

Affiliation:

Stockholms universitet

Start Date:

2019-04-30

End Date:

2020-05-01

Primary Classification:

10402: Physical Chemistry

Webpage:

Allocation

Abstract

Transition-metal perovskite oxides (ABO3) have been extensively studied for the past decades due to their diverse electric and magnetic properties, including ferroelectricity, colossal magnetoresistance and superconductivity. As a consequence of these fascinating properties, these materials have found many applications, such as in photovoltaics, solid-oxide fuel cells and, most notably, in sensors. Furthermore, the properties can be tailored by substitution of the cations (A, B) or by modifying the anion lattice by the introduction of oxygen vacancies or substitution of oxygen by heteroanions [1,2]. Recent studies have demonstrated that reduction of perovskite oxides with metal hydrides can generate new materials (oxyhydrides) with both oxygen vacancies and oxygen sites substituted by hydride anions. These oxyhydrides form either well ordered structures [1,2] or consist of solid solutions of anions (O2- and H-) [3,4] and exhibit peculiar chemical and physical properties. For instance, they can exhibit hydride conduction, or act as Mott insulators. These materials possess potential for application for energy storage and memory devices [2-4]. Therefore, investigations of hydride local environments could further our understanding of the material properties and allow rational design of novel perovskite oxyhydrides with improved characteristics. Most commonly these materials are studied using XRD or QENS methods [4,5], however NMR can offer complementary data. Solid-state NMR is an excellent tool for the study of nuclei electronic environment, but the interpretation of the obtain data is complicated due to the hyperfine interaction with the unpaired electrons of the metal ions. Nevertheless, hybrid density functional theory (DFT) [6] provides a means to calculate paramagnetic NMR shifts in insulators and Knight shifts in metals, thus facilitating the assignment of the NMR spectra. Furthermore, using DFT the electric-field gradient (EFG) tensor principle components can be computed for quadrupolar nuclei. The EFG is particularly sensitive to the local environment of the hydride ion. We expect that this methodology will permit accurate interpretation of 2H NMR spectra of the two different forms of deuterated hydride ion conductor BaTiO3-xHy that have recently been acquired and provide new insights into the oxyhydride structure and their exotic magnetic and electric properties. Therefore, the purpose of this proposal is to gain access to computer resources which will allow us to carry out calculations of paramagnetic NMR shifts and EFG tensor components via DFT. The project is at the current frontier of NMR-based structural material science, since the perovskite oxyhydrides are of great interest in materials science and our newly development NMR experimental techniques have yielded unprecedented information of the hydride anion environments. [1] Yamamoto, T et al. Nat. Commun., 8, 1217, 2017. [2] Katayama, T. et al. J. Appl. Phys., 120, 085305, 2016. [3] Kobayashi, O. J. et al., Nat. Mater., 11, 6, 507-511, 2012. [4] Nedumkandathil, R. et al., ACS Omega, 3, 9, 11426–11438, 2018. [5] Eklöf-Österberg, C. et al., J. Phys. Chem. C, 123, 2019-2030, 2019. [6] Middlemiss, D. S. et al., Chem. Mater., 25, 9, 1723–1734, 2013.