First principles total energy calculations of the structural and electronic properties of YGe2 in AlB2 type structures

We have performed first principles total energy calculations to investigate the structural and electronic properties of bulk YGe2, in AlB2 type configurations. Although the experimental stoichiometry is Y2Ge3, we have also considered the ideal YGe2, and the Y3Ge5 configuration found for rare earth disilicides. Our studies using a unit cell with the ideal AlB2 structure result in a lattice parameter a larger and a c/a ratio smaller than the experimental values. On the other hand, the calculated structural parameters for the configurations with vacancies in the graphitic-like Ge planes are in excellent agreement with experimental values. The introduction of vacancies results in more favorable Y–Y and Ge–Y distances. The densities of states display p (of Ge) and d (of Y) orbital hybridizations, and they show that vacancies play an important role in the stability of the compound.

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