The crystal structure of arsenic at 4.2, 78 and 299°K

The lattice constants and the atomic position parameter, z, of a high purity, low strain, single-crystal of arsenic have been determined. Low extinction reflections of filtered Mo Kα and Ag Kα radiation were used for the determination of z. The Bond precision technique with Mo Kα radiation was used for the determination of the unit-cell dimensions a and c. Average values for a and c in Å, and for z are: 4.2°K z = 0.22764 a = 3.7597 c = 10.4412; 78°K z = 0.22754 a = 3.7595 c = 10.4573; 299±3°K z = 0.22707 a = 3.7598 c = 10.5475. The estimated standard deviation of z is ±0.00004 at 4.2°K, ±0.00002 at 78°K and ±0.00005 at 299°K. The precision of a is estimated to be ±0–0001 Å and that for c to be ±0.0002 Å. The results for As are compared with those reported earlier for Sb and Bi.