Elastic properties and their pressure dependence of rare earth metals

Rare earth metals are of significant importance in engineering and technological applications, and their unique f-electron-related behaviors have attracted widespread interest in condensed matter physics. In this work, we investigate the elastic properties of rare earth metals ranging from Ce to Yb by combining first-principles calculations with systematic data compilation. Taking Ce and Yb as representative cases, we investigate the evolution of their elastic properties under high-pressure conditions (0–15 GPa), and we systematically compare the simulation performances of different f-electron treatment approaches. The results indicate a significant difference in ductility between light and heavy rare earth metals under ambient pressure. Under pressure, the elastic properties of Ce and Yb undergo marked changes in phase transitions. Specifically, the <i>B</i>/<i>G</i> ratio, a key indicator of ductility, decreases from about 2.0 in light lanthanides to around 1.5 in heavy lanthanides, crossing the critical threshold of 1.75. Notably, during the fcc iso-structural phase transition in Ce and the fcc-bcc phase transition in Yb, a significant brittle-ductile transition is observed. These transitions are closely related to the bonding characteristics modulated by atomic number or pressure condition. For instance, as the atomic number increases, the Cauchy pressure (<i>C</i><sub>12</sub>–<i>C</i><sub>44</sub>) decreases with the variation of s and d valence electrons, indicating an enhanced covalent bonding tendency. In addition, this study reveals that simulating f-electrons as core electrons can adequately describe the elastic properties and trends of rare earth metals under ambient pressure. However, when modeling high-pressure structural phase transitions and their related elastic evolution, the method of treating f-electrons as valence electrons and performing electron correlation correction shows better accuracy. The datasets presented in this paper are openly available at <ext-link ext-link-type="uri" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="https://doi.org/10.57760/sciencedb.j00213.00150">https://doi.org/10.57760/sciencedb.j00213.00150</ext-link>.