Study on Remelting of Crystal Under Extreme Conditions

The appearance of the maximum point on the melting curve has so far been considered an anomalous phenomenon found only in a few alkali metals and nonmetals. However, recent ab initio studies have shown that the above event is much more universal than we often think. The core problem is to reach the ultra-high pressure region where the melting gradient begins to change sign from positive to negative. This work requires a huge amount of computational resources. Therefore, we aim to build a simple but effective theoretical model to quickly collect important information about remelting. Our main idea is to combine the moment statistical method with the Lindemann criterion to appropriately describe the crystal melting process through the instability of lattice vibrations. In addition, the Morse pair interaction potential is utilized to parameterize the binding energy between atoms. On that basis, we conducted numerical calculations for W—a typical refractory material with many potential applications. We find that its melting gradient will be zero when the nearest neighbor distance between ions reaches 0.8976 Å which corresponds to a pressure of 1.6533 \(\times\) $\times$ 10⁶ GPa and a temperature of 2.7567 \(\times\) $\times$ 10⁵ K. Our finding is strongly supported by existing simulation results.