Improved X-ray powder diffraction data for orthorhombic phosphorus, S.G. C mca (64) obtained in situ at synthesis conditions of 1.2 GPa and 1100 K, are described. Representative, as synthesized, data include 2.552X, 3.3204, 2.5953, 5.1912, 1.6302, for least-squares unit-cell a=3.3182(6) Å, b=10.3744(18) Å and c=4.3227(9) Å. As an illustration of the quality of the data, the structure was solved from powder XRD and Rietveld refined to give a=3.3199(2) Å, b= 10.3678(4) Å, c=4.3154(2)Å, and V=148.535(12) Å3 with the P atom on 8f (1/2, y,z) with y=0.1044(22) and z=0.9179(7).
