Modulated crystal structure of Pr2SbO2.

The crystal structure of commensurately modulated Pr2SbO2 was solved in the orthorhombic superspace group Immm(0β0)000, q = 3/4b*, a = 13.5790 (15), b = 3.9818 (18), c = 4.0041 (18) Å (T = 40 K) from a crystal twinned by reticular pseudomerohedry applying the twin law (1 0 0, 0 0 1, 0 -1 0), corresponding to a rotation by 90° along the reciprocal a axis. The formation of Zintl-type Sb(2-)-Sb(2-) dumbbells in Pr2(3+)Sb(2-)O2(2-) is considered to be accountable for its semiconducting properties, as observed previously. The space group for the three-dimensional commensurate supercell a = 13.5790 (15), b = 15.9272 (18), c = 4.0041 (18) Å (T = 40 K) is Pmnm.