2017/03/20 by Yangmei Chen, Hua-Yun Geng, Hua Y. Geng +5
Chemistry · Materials Science · Physics and Astronomy · #Atomic physics #Chemistry #Ground state #Hydrogen Storage and Materials #Internal medicine #Lithium (medication) #Nuclear Materials and Properties #Physics #Thermal and Kinetic Analysis #cond-mat.mtrl-sci #cond-mat.other #physics.app-ph #physics.chem-ph #physics.comp-ph
paper · pdf · doi:10.1021/acs.inorgchem.6b02709
published as Inorg. Chem. 56, 3867 (2017) · 34 pages, 15 figures
openalex publication_date 2017/03/20 · arxiv created 2017/05/11 · arxiv updated 2017/05/12 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Hydrogen-rich compounds are important for understanding the dissociation of dense molecular hydrogen, as well as searching for room temperature Bardeen–Cooper–Schrieffer (BCS) superconductors. A recent high pressure experiment reported the successful synthesis of novel insulating lithium polyhydrides above 130 GPa. However, the results are in sharp contrast to a previous theoretical prediction by the PBE functional that around this pressure range all lithium polyhydrides (LiH n ( n = 2–8)) should be metallic. In order to address this discrepancy, we perform an unbiased structure search with first-principles calculation by including the van der Waals interaction that was ignored in the previous prediction to predict the high pressure stable structures of LiH n ( n = 2–11, 13) up to 200 GPa. We reproduce the previously predicted structures, and further find novel compositions that adopt more stable structures. The van der Waals functional (vdW-DF) significantly alters the relative stability of lithium polyhydrides, and predicts that the stable stoichiometries for the ground state should be LiH 2 and LiH 9 at 130–170 GPa, and LiH 2, LiH 8, and LiH 10 at 180–200 GPa. Accurate electronic structure calculation with GW approximation indicates that LiH, LiH 2, LiH 7, and LiH 9 are insulative up to at least 208 GPa, and all other lithium polyhydrides are metallic. The calculated vibron frequencies of these insulating phases are also in accordance with the experimental infrared (IR) data. This reconciliation with the experimental observation suggests that LiH 2, LiH 7, and LiH 9 are the possible candidates for lithium polyhydrides synthesized in that experiment. Our results reinstate the credibility of density functional theory in the description of H-rich compounds, and demonstrate the importance of considering van der Waals interaction in this class of materials.