Atomic distributions of Ag and In in the γ-brass type Ag9In4.

The γ-brass type phase Ag 9 In 4 in the binary Ag–In system has been synthesized by high-temperature method and, the crystal structure has been determined by the means of X-ray diffraction techniques and energy dispersive X-ray spectroscopy. The structure crystallizes in the primitive cubic space group P 4 ‾ 3 m (cP 52) with a cell parameter of ∼ 9.89 Å. The unit cell contains 52 atoms distributed over 8 crystallographically independent positions. Due to weak X-ray scattering contrast between Ag and In, first principle DFT calculations have been carried out to determine the accurate site occupancy pattern of Ag and In in the structure of Ag 9 In 4. The structure can be viewed in terms of two symmetrically inequivalent 26-atom γ-clusters (Ag 22 In 4 and Ag 14 In 12). The density of state (DOS) curve shows a pseudogap near the Fermi level, which endorses the phase stability by Hume-Rothery mechanism due to interaction between the Fermi surface and the Brillouin zone (FS-BZ). Bonding analysis shows that Ag–In contact has the highest contribution in stabilizing the titled phase. The atomic distribution of Ag and In in the structure of Ag 9 In 4 has been addressed by means of structural and theoretical investigation. The accurate site distribution patter in the structure of Ag 9 In 4 is governed by the "bond energy" factor. [Display omitted] • An ordered P -centered γ-brass type phase, Ag 9 In 4 has been synthesized by high temperature synthesis. • The atomic distribution pattern between Ag and In has been investigated by structural and theoretical investigations. • Bonding analysis discerns the structure is mainly stabilized by maximum Ag–In contacts and minimum In–In contacts. • The "coloring" scheme can be rationalized by bond energy as well as size factor. [ABSTRACT FROM AUTHOR]