Structure prediction and stability of novel hydride-based superconductors
||Structure prediction and stability of novel hydride-based superconductors|
||SNIC Medium Compute|
||Ulrich Häussermann <email@example.com>|
||2021-06-01 – 2022-06-01|
||10304 10403 |
The proposed computational activities are meant to support experimental efforts in the synthesis of new hydrogen-rich materials using high pressure techniques. In particular, the experimental program targets ternary hydrides A – X – H (X = Si, Ge, P, S; A = Li, Na, Mg, Sc, Y, La)). We employ in situ diffraction techniques at synchrotron beamlines in order to establish the p,T formation conditions for new, potentially superconducting, hydrogen-rich hydrides and to elucidate pathways for their ambient pressure recovery. Our experimental efforts were fueled by the discovery of a critical temperature as high as 203 K at 150 GPa for H3S (Drozdov et al. (2015) Nature, 525, 73). However, this material is not recoverable and the pressure conditions for superconductivity are far too extreme for any technological significance. The large compositional and structural flexibility of ternary hydrides allows optimization of superconducting properties and provides the possibility for synthesis at comparatively lower pressures, as well as ambient pressure recovery.
The computational activities include the application of crystal structure prediction (CSP) techniques to establish the phase space of the selected A-X-H systems. Predicted compositions and structures will then serve as valuable input for guiding the experiments. The calculations will be done in the pressure range of 0-30 GPa, achievable by experimental techniques. The stability of the obtained compounds with different concentrations of compositing elements then will be checked using Hull line and phonon calculations. For predicted stable phases (p,T)-dependent electronic structure and electron-phonon coupling calculations will be performed.