Compression media anvil cells

A study of RDX behaviour under static ultrahigh pressure (up to 65 GPa), generated by using diamond anvil cells (DACs) using FT-IR spectroscopy and UV-VIS absorption spectroscopy, is a topic of paper [61]. RDX changed its colour into dark red when compressed up to 20 GPa with caesium iodide (Csl), filled as a pressure medium. In this case the intensities of characteristics of IR absorption peaks of RDX decreased as the pressure increased, and did not return to the intensities measured at ambient pressure, after the pressure was unloaded. However, when RDX was compressed alone, its colour changed into yellow at a pressure above 60 GPa. In its UV-VIS absorption spectra the peak shifted from 243.5 nm at ambient pressure to 410 nm at 65.5 GPa. The authors assume that the HOMO-LUMO band gap of this nitramine decreases with increasing pressure [61] which is in line with the opinion of Kuklja and Kunz [59]. 

In HPHT synthesis, a small pressure medium including furnace (heater), sample cell, and thermocouple is compressed in a high pressure apparams. There are two types of high pressure systems used for the synthesis of clathrate and intermetallic compounds, a belt-type apparams and a multi-anvil apparatus. These apparamses are also widely used for geological high pressure smdies and in sim X-ray diffraction smdies using synchrotron radiation under HPHT conditions [18]. 

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