Phase behavior of metals at very high P–T conditions: A review of recent experimental studies

Studies at extreme pressures and temperatures are helpful for understanding the physical properties of the solid state, including such classes of materials as, metals, semiconductors, superconductors, or minerals. In particular, the phase behavior of metals at extreme pressures and temperatures is a challenging problem with many implications for other fields including Earth and planetary sciences. However, despite the efforts performed, the phase behavior of metals at very high pressures (HPs) and temperatures has been proven hard to predict accurately and only a limited number of experimental methods for making measurements in the regime of megabar pressures and thousand degree temperatures exist. In this contribution, we will review recent laser-heated diamond-anvil cell (DAC) studies on the phase behavior of different metals. In particular, we will focus on discussing the results obtained for the alkaline-earth metals, the transition metals, and the rare-earth metals, which we had extensively studied up to 1 Mbar and 4000 K. Differences and similarities of the phase behavior of these elements will be discussed aiming to improve the actual understanding of melting behavior at HP. We will also describe different experimental techniques for obtaining reliable data at simultaneously HP and high temperature employing the laser heated DAC. Drawbacks and advantages of the different techniques are discussed along with recent developments involving X-ray diffraction.