Improved phase diagram of nitrogen up to 85 kbar

A quasi-isochoric scanning method has been used to study the phase diagram of nitrogen from 150 to 550 K and up to 85 kbar in a diamond anvil cell in order to make a comparison with previous measurements of the binary phase diagram He-N₂. It has been confirmed that there is only one solid-solid-fluid triple point in N₂ up to 85 kbar. However, both the δ-β transition line and the melting line have shifted appreciably towards lower pressures. The present experiment shows that, as a result of this, the triple point is located at 555 ± 5 K and 80 ± 2 kbar, which is 20% lower in pressure than previous data.