Title: Predicting the thermodynamic stability of double-perovskite halides from density functional theory

Abstract

Recently, a series of double-perovskite halide compounds such as Cs₂AgBiCl₆ and Cs₂AgBiBr₆ have attracted intensive interest as promising alternatives to the solar absorber material CH₃NH₃PbI₃ because they are Pb-free and may exhibit enhanced stability. The thermodynamic stability of a number of double-perovskite halides has been predicted based on density functional theory (DFT) calculations of compound formation energies. In this paper, we found that the stability prediction can be dependent on the approximations used for the exchange-correlation functionals, e.g., the DFT calculations using the widely used Perdew, Burke, Ernzerhof (PBE) functional predict that Cs₂AgBiBr₆ is thermodynamically unstable against phase-separation into the competing phases such as AgBr, Cs₂AgBr₃, Cs₃Bi₂Br₉, etc., obviously inconsistent with the good stability observed experimentally. The incorrect prediction by the PBE calculation results from its failure to predict the correct ground-state structures of AgBr, AgCl, and CsCl. By contrast, the DFT calculations based on local density approximation, optB86b-vdW, and optB88-vdW functionals predict the ground-state structures of these binary halides correctly. Furthermore, the optB88-vdW functional is found to give the most accurate description of the lattice constants of the double-perovskite halides and their competing phases. Given these two aspects, we suggest that the optB88-vdW functional should be used for predictingmore » thermodynamic stability in the future high-throughput computational material design or the construction of the Materials Genome database for new double-perovskite halides. As a result, using different exchange-correlation functionals has little influence on the dispersion of the conduction and the valence bands near the electronic bandgap; however, the calculated bandgap can be affected indirectly by the optimized lattice constant, which varies for different functionals.« less

Authors:

Han, Dan ^[1]; Zhang, Tao ^[1]; Huang, Menglin ^[1]; Sun, Deyan ^[1]; Du, Mao -Hua  ^[2];

• Search DOE PAGES for author "Du, Mao -Hua"
• Search DOE PAGES for ORCID "0000-0001-8796-167X"
• Search orcid.org for ORCID "0000-0001-8796-167X"

Chen, Shiyou ^[3]

---

+ Show Author Affiliations

1. East China Normal Univ., Shanghai (China)
2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
3. East China Normal Univ., Shanghai (China); Shanxi Univ., Shanxi (China)

Publication Date:

2018-05-24

Research Org.:

Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1440832

Grant/Contract Number:  

AC05-00OR22725

Resource Type:

Accepted Manuscript

Journal Name:

APL Materials

Additional Journal Information:

Journal Volume: 6; Journal Issue: 8; Journal ID: ISSN 2166-532X

Publisher:

American Institute of Physics (AIP)

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE