First-principles calculations, including structural relaxations, were performed with density functional theory (DFT) using the Vienna Ab Initio Simulation Package (VASP) software package. The generalized gradient approximation (GGA) of Perdew-Burke-Ernzerhof (PBE) was used as the exchange correlation func-tional. The core and valence electrons were treated with the projector-augmented wave (PAW) method. A plane-wave energy cutoff of 340 eV was used, and an automatically generated G-centered regular k-point mesh was used to sample the Brillouin zone. Bulk modulus (B) was determined by fitting the Birch-Murnaghan equation of state to a set of total energies computed at different volumes that were expanded and contracted around the equilibrium volume).