High-pressure Forms
The pressure-temperature (P-T) phase diagram of sulfur is complex. Some researchers have used laser illumination of samples and found that perhaps 3 forms can be photo-induced below 20–30 GPa. In a high-pressure study at ambient temperatures, four forms, termed S-II, S-III, S-IV, S-V have been characterized (α-sulfur being S-I). S-II and S-III are polymeric forms, S-IV and S-V are metallic and are superconductors below 10 K and 17 K, respectively.
Read more about this topic: Allotropes Of Sulfur
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