Second group of high-pressure high-temperature lanthanide polyhydride superconductors

Abstract

Rare-earth polyhydrides formed under pressure are promising conventional superconductors, with the critical temperature Tc in compressed LaH10 almost reaching room temperature. Here, we report a systematic computational investigation of the structural and superconducting properties of rare-earth (RE) polyhydrides formed under pressure across the whole lanthanide series. Analyses of the electronic and dynamical properties and electron-phonon coupling interaction for the most hydrogen-rich hydrides REHn (n = 8, 9, 10) that can be stabilized below 400 GPa show that enhanced Tc correlates with a high density of H s-states and low number of RE f-states at the Fermi level. In addition to previously predicted and measured LaH10 and CeH9, we suggest YbH10 and LuH8 as additional potential high-Tc superconducters. They form a 'second island' of high-Tc superconductivity amongst the late lanthanide polyhydrides, with an estimated Tc of 102 K for YbH10 at 250 GPa.

Electronic Structure and Superconductivity of Compressed Metal Tetrahydrides

“…For example, Fm � 3m YbH 10 was calculated to have a T c that was about a factor of two smaller than isotypic LaH 10 at the same pressure. [29] Although it is likely that the evolution of the geometric properties, electronic structure and bonding within I4=mmm BaH 4 would be similar to our findings for CaH 4 and SrH 4 this phase was not studied because unlike the other hydrides discussed in this section, this compound does not lie on the convex hull. [75] Moreover, the only polyhydrides of barium that have been made under high pressure are Ba 8 H 46 [76] and BaH 12 .…”

“…[71] Similarly, a recent study on the REH 8 , REH 9 and REH 10 concluded that a high T c in these phases is correlated with a large number of hydrogenic, and low number of RE f states at E F . [29] In the sections that follow, we will discuss the evolution of the structure, electronic structure and propensity for superconductivity in these phases under pressure. To gauge the bond strengths between the apical hydrogen atoms the negative of the Crystal Orbital Hamilton Population integrated to the Fermi level (À iCOHP) was calculated for the H a À H a pairs.…”

“…[23] These findings have inspired theoretical investigations of the superconducting mechanism, pressure dependence of T c , and anharmonic effects in LaH 10 as well as the isotypic YH 10 phase, [24][25][26][27][28] and the relationship between electronic structure and superconductivity in rare earth (RE) polyhydrides, REH n with n ¼ 8; 9; 10. [29] Another crystalline lattice that is predicted to be ubiquitous among the highpressure alkaline and RE metal hydrides is an I4=mmm symmetry MH 4 phase containing hydridic and quasi-molecular hydrogen atoms with a formula that can be written as M…”

“…. Theoretical studies based upon a priori crystal structure prediction have found that MgH 4 , [30] CaH 4 , [31][32][33] SrH 4 , [34,35] ScH 4 , [18,[36][37][38] YH 4 , [18] ZrH 4 , [30] LaH 4 , [19] CeH 4 , [18,39,40] PrH 4 , [18] NdH 4 , [41] EuH 4 , [42] TbH 4 , [43] ThH 4 , [44] PuH 4 , [45] and all of the REH 4 [29] phases assuming this structure type are thermodynamically stable in their respective pressure ranges. Therefore, this I4=mmm structure may be a universal feature in the phase diagram of most of the compressed alkaline and rare earth, as well as a few transition metal and actinide tetrahydrides under pressure.…”

A study of the application of graphite MALDI to the analysis of lanthanides and deconvolution of the isobaric species observed

“…CG was deposited either by pipette or by using a previously published airbrush application method. 17 Although lanthanide chemistry is a fairly specialist field, there are a number of emerging applications in areas such as proteomics, 18 organometallic and co-ordination chemistry, 19 superconducting materials 20 and in nuclear medicine. 21 Lanthanide salts are readily available and easily handled (apart from promethium which is radioactive) and as such are good candidates as proxies for other more toxic heavy metals as well as for the actinides (many of which are radioactive).…”