13 October 2014 to 7 November 2014
Nordita, Stockholm
Europe/Stockholm timezone

GW/Bethe-Salpeter Equation Calculations of the X-ray Absorption Spectra of Water

24 Oct 2014, 09:00
1h
FB52 (Nordita, Stockholm)

FB52

Nordita, Stockholm

Speaker

Prof. John Rehr (University of Washington)

Description

We calculate x-ray absorption spectra (XAS) of water within a GW/Bethe-Salpeter Equation (BSE) approach using the OCEAN code [1-3]. This hybrid code combines ab initio plane- wave, pseudopotential electronic structure, PAW transition- matrix elements, GW self-energy corrections, and the NIST BSE solver [1]. Due to the computational demands, our previous XAS calculations [2] were limited to 17 molecule super cells. This limitation causes unphysical, size dependent effects in the calculated spectra. In order to treat much larger systems several improvements were necessary [3]: 1) we extended the OCEAN interface to support well-parallelized codes such as QuantumESPRESSO; 2) we implemented an efficient interpolation scheme due to Shirley. We have applied this large-scale GW/BSE approach to 64 molecule unit cell structures of water obtained from classical DFT/MD and PIMD simulations [4]. In comparison with previous work [5], we obtain improved spectra that agree semi-quantitatively with experimental features. The agreement suggests that the 64 molecule unit cell PIMD structures, which are similar to the traditional distorted tetrahedral view, are consistent with experimental observations. [1] J. Vinson et al., PRB 83, 115106 (2011); J. Vinson and J.J. Rehr, PRB 86, 195135 (2012). [2] J. Vinson et al., PRB 85, 045101 (2012). [3] K. Gilmore, J. Vinson, E.L. Shirley, D. Prendergast, J. J. Kas and J. J. Rehr, UW Preprint 2014. [4] J.A. Morrone and R. Car, PRL 101, 017801 (2008). [5] L. Kong et al., PRB 86, 134203 (2012).

Co-authors

F Vila (University of Washington) J Kas (University of Washington) J Vinson (National Institute of Standards and Technology) K Gilmore (European Synchrotron Radiation Facility)

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