Strong anharmonic and quantum effects in Pm(3)over-barn AIH(3) under high pressure: A first-principles study

Article

关键词: TEMPERATURE SUPERCONDUCTIVITY;    CRYSTAL-STRUCTURE;    LANTHANUM;    HYDRIDE;    TRANSITION;    HYDROGEN;   

DOI  :  10.1103/PhysRevB.103.134305

来源: SCIE

【 摘 要 】

Motivated by the absence of experimental superconductivity in the metallic Pm (3) over barn phase of A1H(3) despite the predictions, we reanalyze its vibrational and superconducting properties at pressures P >= 99 GPa making use of first-principles techniques. In our calculations based on the self-consistent harmonic approximation method that treats anharmonicity beyond perturbation theory, we predict a strong anharmonic correction to the phonon spectra and demonstrate that the superconducting critical temperatures predicted in previous calculations based on the harmonic approximation are strongly suppressed by anharmonicity. The electron-phonon coupling concentrates on the lowest-energy hydrogen-character optical modes at the X point of the Brillouin zone. As a consequence of the strong anharmonic enhancement of their frequency, the electron-phonon coupling is suppressed by at least 30%. The suppression in lambda makes T-c smaller than 4.2 K above 120 GPa, which is well consistent with the experimental evidence. Our results underline that metal hydrides with hydrogen atoms in interstitial sites are subject to huge anharmonic effects.

【 授权许可】

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