Sb, trigonal, R3m (No. 166), a = 4.2687(2) A, c = 10.9244(6) A, V = 172.4 Â, Z = 6, R(P) = 0.066, R(I) = 0.059, 7 = 295 K, Ρ = 2.22 GPa. Discussion Structural parameters of antimony at elevated pressures up to 8.5 GPa were determined earlier by means of single crystal X-ray diffraction in diamond anvil cells [1], We re-refined the parameter values in order to gain a quantitative measure for the reliability of full profile refinements using powder patterns measured with synchrotron radiation. The result of the least squares procedure is within three standard deviations identical to the values obtained by single crystal diffraction methods (z = 0.2358(6) at Ρ = 1.5 GPa and ζ = 0.2379(6) at Ρ = 2.66 GPa [ 1 ]) . The resulting interatomic distances of 3 χ 2.895(1) A and 3 χ 3.253(1) Â support the finding that the rhombohedral low-pressure phase approaches a simple cubic arrangement with increasing pressures [1,2]. Table 1. Data collection and handling. Powder: black, size 5 -10/ Angle-dispersive X-ray powder diffraction experiments were performed on ID-9 at ESRF using an image plate detector. The powdered particles were placed in a gasketed diamond anvil high-pressure cell using a small sphere of ruby for pressure calibration and a 4:1 mixture of ethanol and methanol as a pres- sure transmitting medium. Table 2. Atomic coordinates and displacement parameters (in Â).