High-pressure phase diagram of gold from first-principles calculations: Converging to an isotropic atomic stacking order

At 300 K we predicted that Au transits from fcc to dhcp at 231.6 GPa based on the GGA. In general, the stable field of the fcc structure is in good agreement with its experimental data. At 300 K, the dhcp-Au transits to hcp structure at 447.8 GPa. The boundary between fcc and dhcp has a negative slope and the boundary between dhcp and hcp has a positive one, but the slopes of the two boundaries are both very steep. It is also worthy to note that the bcc, I4/mmm and Immm structures are not competitive in energy in the whole pressure and temperature range of interest. Our predicted stable field of hcp structure does not support the experimental results. The LDA shifts the fcc-dhcp phase boundary downwards along the pressure axis, by 90 GPa at most. On the contrary, it shifts the dhcp-hcp phase boundary upwards by 20 GPa or so. Pressure results in an isotropy of atomic stacking order in Au.87