Application of normal probability plot analysis to lutetium orthoborate factors and parameters

The methods of normal probability plot analysis have been applied to two nearly complete sets of structure factors (F_meas) and the corresponding objectively assigned standard deviations (σF_meas) obtained by diffractometer measurement with two different crystals of lutetium orthoborate. The least-squares derived positional and thermal vibration parameters are shown to be too small by a factor of 1.8, and the σF_meas to be overestimated by a factor of 1.55. The two sets of F_meas are found to contain a small but parallel bias. The lattice constants of rhombohedral calcite-type LuBO₃ are measured as a_H = 4.91538±0.00002 Å and c_H = 16.21200±0.00003 Å at 298°K, with six formulas in the unit cell, space group Rc. The Lu–O distance in this six-coordinated Lu compound is 2.240±0.002 Å (corrected standard deviation). The B–O distance in the BO₃ triangular groups is 1.370±0.005 Å. The characteristic Θ temperature is estimated as 446±19°K.