Density functional theory study of bulk platinum monoxide

The ground state electronic structure of platinum monoxide (PtO) has been calculated using density functional theory (DFT) with periodic boundary conditions and Gaussian type orbitals. Several DFT exchange-correlation functionals, including a hybrid functional based on a screened Coulomb potential for exact exchange have been used. Our study reveals that functionals based on the generalized gradient approximation (GGA) or meta-GGA do not give qualitatively different results from those of the local spin density approximation, predicting PtO to be metallic, whereas the hybrid functional predicts a semiconductor with a band gap of $0.86\mathrm{eV}$. A reduced band gap of $0.56\mathrm{eV}$ is found in the oxygen deficient $\mathrm{Pt}{\mathrm{O}}_{0.9}$ system.

Figure 1

Tetragonal PtO unit cell used in periodic boundary conditions (PBC) calculations. Two formula units per cell are necessary for translational symmetry constraints as well as to study the antiferromagnetic state. Platinum is shown in larger spheres.

Figure 2

The total density of states for PtO calculated using LSDA, PBE, and TPSS. The Fermi level is placed at $0\mathrm{eV}$ and marked by a dashed vertical line.

Figure 3

The total density of states, the $d$-partial density of states arising from total $d$ and crystal field splitted $d$ orbitals and $p$-partial density of states arising from O atom are also shown at the TPSS level. The Fermi energy is placed at $0\mathrm{eV}$ and marked by a dashed vertical line.

Figure 4

The total density of states, the $d$-partial density of states arising from total $d$ and crystal field splitted $d$ orbitals and $p$-partial density of states arising from O atom are also shown at the HSE level. The Fermi energy is placed at $0\mathrm{eV}$ and marked by a dashed vertical line.

Figure 5

Band structures of PtO calculated using the LSDA, PBE, TPSS, and HSE functionals. Calculated energy eigenvalues of four highest occupied crystalline orbitals (HOCO) and four lowest unoccupied crystalline orbitals (LUCO), along various high symmetry directions are shown. The $\Gamma$, $\mathbf{X}$ and $\mathbf{M}$ points lie in the central plane of tetragonal Brillouin zone with $k_x$ and $k_y$ coordinate of (0,0), $(2\pi ∕a,0)$, and $(2\pi ∕a,2\pi ∕a)$, respectively. A horizontal broken line denotes Fermi energy. The minimum band gap is located at $\mathbf{M}$ point in the case of hybrid calculation.

Figure 6

Effects of oxygen vacancies on total density of states. The total density of states for oxygen deficient ${\mathrm{Pt}}_8{\mathrm{O}}_7$ $(\approx \mathrm{Pt}{\mathrm{O}}_{0.9})$ and stoichiometric ${\mathrm{Pt}}_8{\mathrm{O}}_8$ (or $\mathrm{Pt}{\mathrm{O}}_{1.0}$) calculated using the HSE level. The Fermi energy is placed at $0\mathrm{eV}$ and marked by a dashed vertical line.