Abstract:
Lanthanum hydride compounds LaH3 become stabilized by yttrium substitution under the influence of
moderate pressure. Novel materials with a wide range of changes in the structural properties as
a function of hydrogen are investigated by means of the first-principles cluster expansion technique.
Herein, the new compounds La1 xYxH3, where 0 # x # 1, are determined to adopt tetragonal structures
under high-pressure with the compositions La0.8Y0.2H3, La0.75Y0.25H3, and La0.5Y0.5H3. The corresponding
thermodynamic and dynamical stabilities of the predicted phases are confirmed by a series of
calculations including, for example, phonon dispersion, electronic band structure, and other electronic
characteristics. According to the band characteristics, all hydrides except that of I41/amd symmetry are
semiconductors. The tetragonal La0.5Y0.5H3 phase is found to become semi-metallic, as confirmed by
adopting the modified Becke–Johnson exchange potential. The physical origins of the semiconductor
properties in these stable hydrides are discussed in detail. Our findings provide a deeper insight into this
class of rare-earth ternary hydrides.
