Optical response of the sodium alanate system: GW(0)-BSE calculations and thin film measurements

Autor(en)

M. J. Van Setten, Robin Gremaud, Geert Brocks, Bernard Dam, Georg Kresse, Gilles de Wijs

Abstrakt

We calculate from first principles the optical spectra of the hydrides in the sodium alanate hydrogen storage system: NaH, NaAlH4, and Na3AlH6. In particular we study the effects of systematic improvements of the theoretical description. To benchmark the calculations we also measure the optical response of a thin film of NaH. The simplest calculated dielectric functions are based upon independent electrons and holes, whose spectrum is obtained at the G(0)W(0) level. Successive improvements consist of including partial self-consistency (so-called GW(0)) and account for excitonic effects, using the Bethe-Salpeter equation (BSE). Each improvement gives a sizable blue shift or red shift of the dielectric functions, but conserves the trend in the optical gap among different materials. Whereas these shifts partially cancel at the highest (GW(0)-BSE) level of approximation, the shape of the dielectric functions is strongly modified by excitonic effects. Calculations at the GW(0)-BSE level give a good agreement with the dielectric function of NaH extracted from the measurements. It demonstrates that the approach can be used for a quantitative interpretation of spectra in novel hydrogen storage materials obtained via, e. g., hydrogenography.

Organisation(en)

Computergestützte Materialphysik

Externe Organisation(en)

Radboud University, Vrije Universiteit Amsterdam, University of Twente, Delft University of Technology

Journal

Physical Review B

Band

83

Anzahl der Seiten

6

ISSN

1098-0121

DOI

https://doi.org/10.1103/PhysRevB.83.035422

Publikationsdatum

2011

Peer-reviewed

Ja

ÖFOS 2012

103018 Materialphysik

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/4188b8c7-4290-4ef1-b160-1bfa9ca35571