Towards understanding the dissolving behaviors of oxygen at finite temperature in Au and Ag: First-principles total energy and phonon spectrum calculations

By first-principles total energy and vibration spectrum calculations, we predict the impurity oxygen (O) dissolving behaviors at-finite temperature in Au and Ag. The temperature effect is considered by the lattice expansion and phonon vibration energy. An O atom is invariably preferable to stay at the tetrahedral interstitial site rather than the octahedral interstitial site over the whole temperature regime 200-1200 K in two metals. The O solution energy referring to the static O chemical potential μO (T= 0 K) decreases with temperature, while the O solution energy in reference to the temperature-dependent O chemical potential μO (T≠0 K) increases with the increasing temperature. Meanwhile, phonon vibration energy plays a crucial role in the O dissolving behavior with temperature. Based on the obtained temperature-dependent O solution energy, we predict the O concentration over the temperature range 200-1200 K in both metals. Due to that the above data of O dissolving behaviors are rather scarce in both experiment and calculation, our theoretical predictions can provide a very useful reference for purification of Au and Ag as noble metals in industry.