High-pressure synthesis and crystal structure of SrGa4As4

Strontium tetragallate(II,III) tetraarsenide, SrGa4As4, was synthesized in a Walker-type multianvil apparatus under high-pressure/high-temperature conditions of 8 GPa and 1573 K. The compound crystallizes in a new structure type (P3(2)21, Z = 3) as a three-dimensional (3D) framework of corner-sharing SrAs8 quadratic antiprisms with strontium situated on a twofold rotation axis (Wyckoff position 3b). This arrangement is surrounded by a 3D framework which can be described as alternately stacked layers of either condensed (GaAs4)-As-III tetrahedra or honeycomb-like layers built up from distorted ethane-like (Ga2As6)-As-II units comprising Ga-Ga bonds.