Abstract
Single crystals of As2Se3 were prepared hydrothermally. The crystal structure was determined by using the intensities of 1014 independent reflections, measured on a computer-controlled single-crystal diffractometer. The cell constants, refined by least-squares, are: a = 12.0774(4), b = 9.9037(6), c = 4.2835(6) Å, β = 90.458°(9); Z = 4; space group P21/n.
The structure was solved by using MULTAN combined with successive Fourier syntheses. The final R value was 0.038 and Rw = 0.037.
Each As atom is surrounded by a composite polyhedron of seven Se atoms, consisting of a tetragonal pyramid and a triangular prism, one face of which coincides with the base of the pyramid. Two centrosymmetrically equivalent composite polyhedra are linked by a common prismatic face, forming thus a double composite polyhedron, which is further linked on either side to two centrosymmetrically equivalent composite polyhedra through common prismatic faces. Thus a block of four composite polyhedra is formed. This combination of the polyhedra is repeated along the c axis, forming infinite chains. These chains are further linked to four similar adjacent chains by common Se, Se edges.
