Impact of ionic quantum fluctuations on the thermodynamic stability and superconductivity of LaBH8

Francesco Belli; Ion Errea

doi:10.1103/PhysRevB.106.134509

← Back to search

Impact of ionic quantum fluctuations on the thermodynamic stability and superconductivity of LaBH8

Francesco Belli, Ion Errea

DOI 10.1103/PhysRevB.106.134509 · Physical Review B

T1

Active bibliographic source — not scientific approval

Bibliographic access preserves source history; it does not approve extracted materials or validate reported claims. Review warnings on each occurrence separately.

Abstract

The recent prediction of a metastable high-symmetry Fm3¯m phase of LaBH8 gives hopes to reach high superconducting critical temperatures at affordable pressures among ternary hydrogen-rich compounds. Making use of first-principles calculations within density functional theory and the stochastic self-consistent harmonic approximation, we determine that ionic quantum fluctuations drive the system dynamically unstable below 77 GPa, a much higher pressure than the 45 GPa expected classically. Quantum anharmonic effects stretch the covalent B-H bond in the BH8 units of the structure, and consequently, soften all hydrogen-character modes. Above 77 GPa Fm3¯mLaBH8 remains metastable, and interestingly, its superconducting critical temperature is largely enhanced by quantum anharmonic effects, reaching critical temperatures around 160 K at the verge of the dynamical instability. Our results suggest that low-pressure metastable phases with covalently bonded symmetric XH8 units will be destabilized by ionic quantum fluctuations.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
LaBH8 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	160	77 GPa	unknown
LaBH8 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	120	40 GPa	unknown
H3S Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	200	150 GPa	unknown
YH6 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	250	Pressure not reported	unknown
LaH10 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	250	Pressure not reported	unknown
YH9 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	250	Pressure not reported	unknown
RbH12 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	115	50 GPa	unknown
MgLi2H16 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	450	250 GPa	unknown
BaSiH8 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
SrSiH8 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown