In this paper, we present a study of the structural stability of BaSi 2 under high pressure based on first-principles calculations using the projector augmented wave method and generalized gradient approximation as implemented in the ABINIT code. The equations of state of three known polymorphs of BaSi 2 and four candidate structures are calculated along with their structural parameters and their enthalpies of formation. A new polymorph of BaSi 2, not yet reported experimentally, is found to be more stable than all the other structures at high pressure and 0 K. It corresponds to the MgZn 2-type (h) hexagonal structure with hP12 Pearson symbol (space group: P63/mmc. The stiffness coefficients Bij and elastic properties including bulk modulus B0 with its first and second pressure derivative (B′, B′′), Young's modulus (E) and Poisson's ratio (ν) are computed using the stress–strain method.
In the present work, based on first-principles calculations, we show that it is possible to obtain a new high pressure polymorph of the CaSi 2 compound with a Laves structure. It corresponds to the MgCu 2 -type (C15) which is one of the three most important Laves phases. We also show that the two other structures, MgNi 2 -and MgZn 2 -types are very competitive energetically and are possible candidates for finite temperature investigations.
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