Lattice dynamic stability and electronic structures of ternary hydrides La(1−x)Y(x)H(3)via first-principles cluster expansion

Lanthanum hydride compounds LaH(3) 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 La(1−x)Y(x)H(3), where 0 ≤ x ≤ 1, are determined to adopt tetragonal structures under high-pressure with the compositions La(0.8)Y(0.2)H(3), La(0.75)Y(0.25)H(3), and La(0.5)Y(0.5)H(3). 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 I4(1)/amd symmetry are semiconductors. The tetragonal La(0.5)Y(0.5)H(3) 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.