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Introduction and properties

PtO2 exists in three crystalline phases, α-PtO2, β-PtO2 and a theoretical phase β’-PtO2. Unlike α-PtO2 and other Group 8 metal dioxides, β-PtO2 has an orthorhombic CaCl2 -structure. β-PtO2 is a black, highly insoluble solid, and it is the most stable out of the PtO2 -variations under standard temperature and pressure. [1][2]Stability of the peculiar orthorhombic crystal structure of β-PtO2 is due to strong hybridization between 2p-orbital of oxygen and 5d-orbital of platinum. When the densities of states curves are drawn for both β-PtO2 (CaCl2) and β’-PtO2 (rutile), an absence of a peak at the fermi level can be observed for β-PtO2. This results in a pseudo-gap in the fermi level, possibly causing interesting properties. [3]However, there is currently very little experimental data on β-PtO2. Some physical properties of β-PtO2 are listed in table 1.

Table 1. Properties of β-PtO2 [4]

Molecular weight [u]


Density [g/cm3]


Chemical formula


Bulk modulus [GPa]


Band gap (theoretical) [eV]



β-PtO2 crystallizes in the orthorhombic CaCl2 -structure, which is similar to a tetragonal rutile structure, but with small distortions in the directions of a- and b- axes. The tetragonal rutile structure could in theory be obtained when β-PtO2 is heated over 1240 K, resulting in a variation called β’-PtO2[1][6]In β-PtO2, the each Pt atom is coordinated to six O atoms and each O atom to three Pt atoms. [3] The structural information of β-PtO2 is listed in table 2, and the structure is illustrated in figures 1 and 3. A comparison between orthorombic CaCl2 structure and tetragonal rutile structure is shown in figure 2. The simulated XRD powder pattern is shown in figure 4. 

Table 2.  Structural information of β-PtO2 [4]

Space group (Space group number)

Pnnm (58)

Crystal system


Structure type


Unit cell volume [Å3]


Lattice parameters [Å]

a = 4.484

b = 4.536

c = 3.136

α = β = γ = 90°



ICSD code202407

Figure 1. Structure of β-PtO2, on the left ball-stick model (ionic radii), on the right polyhedral model (atomic radii). Red balls represent oxygen, gray balls represent platinum. (Figure: Sini Suurnäkki)

Figure 2. Comparison between CaCl2- and rutile-structure. (Figure: Sini Suurnäkki)

Figure 3. Structure of β-PtO2 viewed from a-, b-, and c- axes, respectively. Red balls represent oxygen, gray balls represent platinum. (Figure: Sini Suurnäkki)

Figure 4. XRD powder pattern of β-PtO2. (Figure: Sini Suurnäkki)


Single crystals can be obtained via high pressure synthesis. Before inventing high pressure synthesis, the precise crystal structure β-PtO2 was unknown, because it could only be synthesized in powder form. β-PtO2 crystals have been synthesized in a temperature of 1500 °C and pressure of 4 kbar, from Pt – KClO3 -mixtures.[4]


1. 1 2

Q, Chen, W. Li, & Y. Yang. β-PtO 2: Phononic, thermodynamic, and elastic properties derived from first-principles calculations. Front. Phys, 2019, 14(5), 53604 (

2. 1

O. Muller, & R. Roy. Formation and stability of the platinum and rhodium oxides at high oxygen pressures and the structures of Pt3O4, β-PtO2 and RhO2. Journal of The Less-Common Metals, 1968, 16(2), 129–146 (

3. 1 2 3

R. Wu, & W. H. Weber. The mechanism of the rutile-to-CaCl2 phase transition: RuO2 and β-PtO2. Journal of Physics: Condensed Matter, 2000, 12(30), 6725 (

4. 1 2 3

K. J. Range, F. Rau, U. Klement, & A. M. Heyns. β-PtO2: High pressure synthesis of single crystals and structure refinement. Materials Research Bulletin, 1987, 22(11), 1541–1547 (

5. 1

Y. Yang, O. Sugino & T. Ohno. Band gap of β-PtO2 from first-principles. AIP Advances, 2012, 2(2), 022172 (

6. 1

W. H. Weber, G. H. Graham, J. R. McBride, Raman spectrum of b-PtO2: Evidence for the D122h-to-D144h phase transition, Phys. Rev., 1990, B 42, 10969 (

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