Electronic structure and structural stability of LaAl2 and LaAl3—A comparative study

The large structural stability regime of LaAl2 and LaAl3 as a function of pressure is investigated by the band structure calculations using the FP-LAPW method. An earlier experimental study has revealed that there is no structural phase transition at ∼35 and ∼30 GPa for LaAl2 and LaAl3, respectively. Our calculations indicate that in the density of states curve of LaAl2, the Fermi level (EF) lies in a slope between bonding maxima and antibonding minima. At high pressures the EF moves slightly towards the valley, but this shifting does not affect its structural stability. In LaAl3, the EF falls in a flat region in the density of states and does not move even up to 33 GPa. The band dispersion curves for both the compounds show movement of bands under the influence of pressure. Some of them cross the Fermi level leading to so called Lifshitz transitions. However, it is seen that these electronic changes do not manifest into any volume anomaly in LaAl3 under pressure. Our study clearly shows that the density of states behavior for LaAl2 and LaAl3 satisfies the Yamashita–Asano criterion for structural stability. The theoretical equations of state, bulk modulus and its pressure derivative values are compared with the experimental values.