Study of the anisotropy of α-³³S single crystal thermal expansion

A technique for arbitrary symmetry crystals unit cell parameters refining on modern single-crystal diffractometers is described. The technique is based on the 2D detector position calibration. The elementary orthorhombic unit cell parameters of the α-³³S single crystal have been refined. The anisotropy of parameters changes in the range of 90–350 K has been studied. It is shown that the relative increase in parameter c is 6.4%. The obtained dependences are approximated by second–third degree polynomials. The absolute increase in cell volume is 138.4 A3, and the relative increase is 4.3%. The temperature dependencies of the thermal expansion tensor elements has been refined. The coefficients of α-³³S thermal expansion tensor at the room temperature are: α₁₁ = 15.35 × 10^–5, α₂₂ = 8.56 × 10^–5, α₃₃ = 9.12 × 10^–5 К^–1.