Structures and electronic properties of platinum nitride by density functional theory

We present the results of ground state electronic structure calculations of the zinc-blende and rocksalt phases of binary platinum nitride (PtN) using density functional theory. Several exchange-correlation functionals including the local spin density approximations, generalized gradient approximations (GGA), a nonempirical meta-GGA, and a screened Coulomb hybrid functional have been employed. We use Gaussian type orbitals within the framework of periodic boundary conditions. Our results confirm earlier findings, in that the zinc-blende structure of PtN is energetically more stable than the rocksalt structure. The predicted energy difference between the two phases is rather small with the more elaborate functionals. Both phases are predicted to be metallic and extended Pt $d\text{−}\mathrm{N}$ $p$ hybridizations are found in both of them. We have also calculated the phase transition pressure between both phases. The bulk modulus of the zinc-blend phase of PtN is significantly higher than that of bulk platinum.

Figure 1

(Color online) Unit-cell for the zinc-blende and rocksalt structures. Darker spheres denote platinum atoms. Tetrahedral and octahedral environments are apparent from the atomic orientations.

Figure 2

Total energy (a.u. per unit cell) vs volume $\left({\mathrm{\AA }}^3\right)$ for the zinc-blende and the rocksalt phases of PtN with the LSDA, PBE, TPSS, and HSE functionals. The fitted curves are obtained using Birch-Murnaghan equation of states. Transition pressures are calculated from the common tangents connecting two curves at each level of theory.

Figure 3

The total density of states (DOS) of the zinc-blende and the rocksalt phases of PtN calculated using PBE and HSE functionals. The Fermi level is placed at $0\mathrm{eV}$ and marked by a dashed vertical line.

Figure 4

The total and partial density of states (DOS) for PtN calculated using the HSE functional for the zinc-blende phase (left figure) and the rocksalt phase (right figure). The Fermi level is placed at $0\mathrm{eV}$ and marked by a dashed vertical line in each case.