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.