First-principles calculation for elastic constantsof α-ScDx(D=H, He)

The elastic constants of α-ScH x (x=0, 1/4, 1/8, 1/32) and α-ScHe x (x=0, 1/4, 1/8, 1/32) are studied by the first-principles method. It is found that the addition of hydrogen to the scandium has an effect greatly different from the addition of helium to this rare-earth metal. The elastic constants of the α-ScH x system almost increase with hydrogen concentration increasing, which is in agreement with the experimental observation. Whereas, in the case of α-ScHe x system, the elastic constants almost decrease with the increase of helium concentration.