| Popis: |
The anisotropic compressibility behavior of hexagonal Selenium has been determined by high pressure x‐ray diffraction and also by high pressure neutron (time‐of‐flight) methods up to 52 kbars. The coefficients are: a‐axis 31.9 ± 7, c‐axis −14.3 ± 4, Volume 49.7 ± 15 kbars−1×10−4. The c‐axis expands under pressure, where it is known that the c‐axis contracts with increase cf temperature. From measurements of the intensities of the diffracted beams, the changes of the Se–Se bond lengths and bond angle with pressure have been measured. The bond angle increases from 102.5° at room temperature and pressure to 105.7° at 52 kbars. The anisotropic behavior can be explained by the bond angles along the chain opening up with increase of pressure, the bond lengths along the chains remaining essentially constant and the distances between the chains decreasing markedly. |
