Structural refinements of high-pressure phases in germanium dioxide

Recently, there has been substantial interest in the new high-pressure polymorphs of GeO₂ synthesized in the laboratory. Previous investigators reported the synthesis of `CaCl<sub>2</sub>-type', `α-PbO₂-type' and `pyrite-type (modified-fluorite-type)' GeO₂ at pressures of 30–130 GPa in laser-heated diamond anvil cells. In order to provide definitive information about the new high-pressure polymorphs, we performed Rietveld refinements of the structures. The structure refinements confirm that two of these high-pressure phases do have the α-PbO₂-type and pyrite-type (modified-fluorite-type) structures.

Computing details

(I_phase_1) germanium dioxide

Crystal data

GeO2	b = 4.2024 (7) Å
Mr = 104.61	c = 2.8039 (4) Å
Orthorhombic, Pnnm	V = 50.08 (1) Å^3
a = 4.2499 (7) Å	Z = 2

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Biso*/Beq
Ge1	0.0	0.0	0.0	0.35*
O1	0.304 (5)	0.292 (6)	0.0	0.35*

(I_phase_2) platinum

Crystal data

Pt	a = 3.8072 (6) Å
Mr = 195.08	V = 55.19 (2) Å^3
Cubic, Fm3m	Z = 4

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Biso*/Beq
Pt1	0.0	0.0	0.0	1.0*

(II_phase_1) germanium dioxide

Crystal data

GeO2	b = 5.0269 (6) Å
Mr = 104.61	c = 4.5223 (6) Å
Orthorhombic, Pbcn	V = 92.11 (2) Å^3
a = 4.0519 (6) Å	Z = 4

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Biso*/Beq
Ge1	0.0	0.169 (1)	0.25	2.9 (7)*
O1	0.211 (5)	0.895 (3)	0.400 (2)	2.9 (7)*

(II_phase_2) sodium chloride

Crystal data

ClNa	a = 2.8600 (3) Å
Mr = 58.44	V = 23.39 (1) Å^3
Cubic, Pm3m	Z = 1

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Biso*/Beq
Na1	0.0	0.0	0.0	0.983*
Cl1	0.5	0.5	0.5	0.983*

(II_phase_3) platinum

Crystal data

Pt	a = 3.7381 (4) Å
Mr = 195.08	V = 52.23 (1) Å^3
Cubic, Fm3m	Z = 4

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Biso*/Beq
Pt1	0.0	0.0	0.0	0.983*

(III_phase_1) germanium dioxide

Crystal data

GeO2	a = 4.3365 (15) Å
Mr = 104.61	V = 81.55 (5) Å^3
Cubic, Pa3	Z = 4

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Biso*/Beq
Ge1	0.0	0.0	0.0	0.446 (9)*
O1	0.3417 (16)	0.3417 (16)	0.3417 (16)	0.446 (9)*

(III_phase_2) rhenium

Crystal data

Re	c = 4.162 (9) Å
Mr = 186.21	V = 24.42 (6) Å^3
Hexagonal, P63/mmc	Z = 2
a = 2.6029 (16) Å

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Biso*/Beq
Re1	0.33333	0.66667	0.25	0.446 (9)*

(III_phase_3) platinum

Crystal data

Pt	a = 3.647 (1) Å
Mr = 195.08	V = 48.51 (2) Å^3
Cubic, Fm3m	Z = 4

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Biso*/Beq
Pt1	0.0	0.0	0.0	0.446 (9)*