Stabilization and electronic topological transition of hydrogen-rich metal Li5MoH11 under high pressures from first-principles predictions

Abstract

Regarded as doped binary hydrides, ternary hydrides have recently become the subject of investigation since they are deemed to be metallic under pressure and possibly potentially high-temperature superconductors. Herein, the candidate structure of Li5MoH11 is predicted by exploiting the evolutionary searching. Its high-pressure phase adopts a hexagonal structure with P63/mcm space group. We used first-principles calculations including the zero-point energy to investigate the structures up to 200 GPa and found that the P63cm structure transforms into the P63/mcm structure at 48 GPa. Phonon calculations confirm that the P63/mcm structure is dynamically stable. Its stability is mainly attributed to the isostructural second-order phase transition. Our calculations reveal the electronic topological transition displaying an isostructural second-order phase transition at 160 GPa as well as the topology of its Fermi surfaces. We used the projected crystal orbital Hamilton population (pCOHP) to examine the nature of the chemical bonding and demonstrated that the results obtained from the pCOHP calculation are associated with the electronic band structure and electronic localized function.

Semiconducting phase of hafnium dioxide under high pressure: a theoretical studied by quasi-particle GW calculations

“…The possibility of finding an electron in the neighboring space of HfO 2 can be measured by the electron localization function (ELF) [41], as reported in Figure 2, where the structure of HfO 2 is presented as shown in Figure 2 (a). The tendency of ELF in HfO 2 is described by the uniform distribution of electron gas with the same density [31,32,42,43,44,45,46]. For the P4/nmm structure, the calculated ELF reveals a set of chemical bonding at the pressure of 150 GPa.…”

Superconducting ternary hydrides under high pressure

“…Therefore, Li 2 MgH 16 shows a superhigh T c up to 430–473 K with extremely strong electron–phonon coupling ( λ = 4) at 250 GPa, in which half of total λ is contributed by the bending modes of atomic H 42 . In contrast, the high‐pressure phase of Li 5 MoH 11 with P 6 3 / mcm symmetry, consisting of face‐shared MoH 12 icosahedra and vertex‐shared HLi 5 trigonal bipyramids, has a weak EPC‐induced T c of 6.5 K at 160 GPa due to low DOS at the Fermi level and the isolated H atoms (the nearest H–H distance is larger than 1.44 Å) 66,111 …”

“…110 Therefore, Li 2 MgH 16 shows a superhigh T c up to 430-473 K with extremely strong electron-phonon coupling (λ = 4) at 250 GPa, in which half of total λ is contributed by the bending modes of atomic H. 42 In contrast, the high-pressure phase of Li 5 MoH 11 with P6 3 /mcm symmetry, consisting of faceshared MoH 12 icosahedra and vertex-shared HLi 5 trigonal bipyramids, has a weak EPC-induced T c of 6.5 K at 160 GPa due to low DOS at the Fermi level and the isolated H atoms (the nearest H-H distance is larger than 1.44 Å). 66,111 On the other hand, Mg can also form H-rich STHs with other metal elements such as Pm-3 MgGeH 6 for Ge and Pmn2 1 MgVH 6 for V, respectively. MgGeH 6 (Figure 5b), lying on the convex hull at 200-300 GPa, shows H-dominated metallicity and significant "flat band-steep band" feature near the Fermi level, leading to strong EPC with 50% from H-derived high frequency.…”

A first-principles study of superconductivity on RbH by doping without applied pressure

“…Furthermore, it is well known that a trustworthy criterion to reach a high T c in hydride materials is a specific combination of strong covalent bonding between hydrogen and other elements of the compound, and the presence of high-frequency modes in the phonon spectrum [7]. On that wise, theoretical calculations have allowed the prediction of the electronic, dynamic and electronphonon (el-ph) coupling properties of hydrogen-rich compounds at high pressures; leading to promising SC systems with T c near room temperature [8][9][10][11][12][13][14]. One of them concluded that in the observed T c evolution as a function of pressure, the role of the energy-dependence on the density of states at the Fermi level, N (0), is crucial for the proper analysis and description of the superconducting state on high-T c metal hydrides as H 3 S, by considering its van Hove singularities [8].…”