High-pressure synthesis and crystal structure of SrGa4As4

Edited by M. Weil, Vienna University of Technology, Austria (Received 13 September 2019; accepted 4 October 2019; online 22 October 2019) 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 (P3221, 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 GaIIIAs4 tetra­hedra or honeycomb-like layers built up from distorted ethane-like GaII2As6 units com­prising Ga—Ga bonds.