Abstract
High pressure structure, stability, metallization, and superconductivity of PbH4(H2)2, a H2-containing compound combining one of the heaviest elements with the lightest element, are investigated by the first-principles calculations. The metallic character is found over the whole studied pressure range, although PbH4(H2)2 is metastable and easily decompose at low pressure. The decomposition pressure point of 133 GPa is predicted above which PbH4(H2)2 is stable both thermodynamically and dynamically with the C2/m symmetry. Interestedly, all hydrogen atoms pairwise couple into H2 quasi-molecules and remain this style up to 400 GPa in the C2/m structure. At high-pressure, PbH4(H2)2 tends to form the Pb-H2 alloy. The superconductivity of Tc firstly rising and then falling is observed in the C2/m PbH4(H2)2. The maximum of Tc is about 107 K at 230 GPa. The softening of intermediate-frequency phonon induced by more inserted H2 molecules is the main origin of the high Tc. The results obtained represent a significant step toward the understanding of the high pressure behavior of metallic hydrogen and hydrogen-rich materials, which is helpful for obtaining the higher Tc.
Highlights
Units exist in the high-pressure structures of GeH4 and SnH4
The decomposition pressure of 133 GPa is much lower than the metallization pressure of solid hydrogen, which is reached in experiments by diamond-anvil techniques
By combining with the phonon density of states (PhDOS) projected on atoms shown in Fig. 7a, in the case of 200 GPa, we find that the low-frequency vibration below 215 cm−1 mainly come from the vibrations Pb atoms
Summary
Units exist in the high-pressure structures of GeH4 and SnH4. And these H2 units have been found to contribute significantly to the superconductivity. Following the experimental observation[24], we have theoretically investigated the structural, phase transition, metallization, and superconductivity of GeH4(H2)[2] under pressure[25,26]. The predicted Tc of GeH4(H2)[2] is close to 100 K at 250 GPa, higher than that of GeH4 These results inevitably encourage us further to seek for high-temperature superconductors and study the superconductivity in these H2-containing compounds. Zaleski-Ejgierd et al theoretically investigated the structure and the stability of PbH4 under high pressure[31]. They found that PbH4 is stable thermodynamically above 132 GPa, in forms of Imma (132–296 GPa) and Ibam (> 296 GPa) space groups. The H2-H2 coupling under high pressure figures out the different superconducting mechanism
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.