Incorporation of vanadium(V) into the rutile-type phase of GeO₂: the solid solution Ge_0.74V_0.21□_0.05O₂

The title compound, γ-vanadium germanium oxide, was prepared as polycrystalline material by conventional solid-state reactions starting from α-quartz-type GeO₂ and V₂O₅ in a K₂CO₃ flux at 1123 K. Some of the Ge⁴⁺ cations were replaced by V⁵⁺, leading to a rutile-type phase where charge neutrality is accomplished by the presence of vacancies. X-ray photoelectron spectroscopy (XPS) confirms the presence of V⁵⁺ in this compound. Its crystal structure was refined from laboratory X-ray powder data using the Rietveld method and is composed of corner- and edge-sharing MO₆ octa­hedra where the metal positions M are statistically occupied by Ge and V. The four equatorial MO bonds lying in the (110) plane are 0.023Å shorter than the two axial bonds.

Key indicators

• Powder X-ray study
• T = 295 K
• Mean [sigma]() = 0.000 Å
• Disorder in main residue
• R factor = 0.000
• wR factor = 0.000
• Data-to-parameter ratio = 0.0

checkCIF/PLATON results

No syntax errors found



Alert level B
PLAT301_ALERT_3_B Main Residue  Disorder .........................      29.00 Perc.

Alert level C
REFI015_ALERT_1_C  _refine_ls_shift/su_max is missing
            Maximum shift/s.u. ratio after final refinement cycle.
            The following tests will not be performed
            SHFSU_01
REFI023_ALERT_1_C  _refine_diff_density_max is missing
            Maximum value of final difference map (e A-3).
            The following tests will not be performed
            DIFMN_01,DIFMX_01,DIFMX_02
REFI024_ALERT_1_C  _refine_diff_density_min is missing
            Minimum value of final difference map (e A-3).
            The following tests will not be performed
            DIFMN_01,DIFMN_02,DIFMN_03
PLAT041_ALERT_1_C Calc. and Rep. SumFormula Strings    Differ ....          ?
PLAT042_ALERT_1_C Calc. and Rep. MoietyFormula Strings Differ ....          ?
PLAT045_ALERT_1_C Calculated and Reported Z Differ by ............       0.50 Ratio
PLAT077_ALERT_4_C Unitcell contains non-integer number of atoms ..          ?
PLAT180_ALERT_3_C Check Cell Rounding: # of Values Ending with 0 =          3
PLAT799_ALERT_4_C Numeric Label on Displacement Par. Record ......          ?

   0 ALERT level A = In general: serious problem
   1 ALERT level B = Potentially serious problem
   9 ALERT level C = Check and explain
   0 ALERT level G = General alerts; check

   6 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   0 ALERT type 2 Indicator that the structure model may be wrong or deficient
   2 ALERT type 3 Indicator that the structure quality may be low
   2 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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Computing details

Data collection: DIFFRAC/AT (Siemens, 1993); cell refinement: FULLPROF (Rodríguez-Carvajal, 2001; data reduction: FULLPROF; program(s) used to solve structure: coordinates taken from an isotypic compound; program(s) used to refine structure: FULLPROF; molecular graphics: DIAMOND (Crystal Impact, 2005); software used to prepare material for publication: FULLPROF.

γ-vanadium germanium oxide

Crystal data

Ge0.74V0.21O2	Z = 2
Mr = 96.43	F(000) = 88.1
Tetragonal, P42/mnm	Dx = 5.77 Mg m^−3
Hall symbol: -P 4n 2n	Cu Kα radiation, λ = 1.54175 Å
a = 4.4001 (1) Å	T = 295 K
c = 2.8670 (1) Å	brown
V = 55.51 (1) Å^3	flat_sheet, 20 × 20 mm

Data collection

Bruker Advance D8 diffractometer	Data collection mode: reflection
Radiation source: sealed X-ray tube, Cu Kα	Scan method: step
Graphite monochromator	2θmin = 5°, 2θmax = 110°, 2θstep = 0.02°
Specimen mounting: packed powder sample container

Refinement

Least-squares matrix: full with fixed elements per cycle	5251 data points
Rp = 0.05	Profile function: pseudo-Voigt modified by Thompson et al. (1987)
Rwp = 0.07	18 parameters
Rexp = 0.03	Weighting scheme based on measured s.u.'s
RBragg = 0.02	Background function: The background was refined first by means of a linear interpolation between 100 background points with refinable heights. At the end of the refinement, the values for all of these heights of the background were fixed.
R(F^2) = 0.02

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

	x	y	z	Uiso*/Ueq	Occ. (<1)
V	0.00000	0.00000	0.00000	0.0053 (1)	0.21 (2)
Ge	0.00000	0.00000	0.00000	0.0053 (1)	0.74 (2)
O	0.3054 (3)	0.3054 (3)	0.00000	0.0025 (1)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
?	?	?	?	?	?	?

Geometric parameters (Å, º)

Ge—O	1.900 (1)	Ge—O^i	1.877 (1)
O—Ge—O^i	90.00 (8)

Symmetry code: (i) −y+1/2, x−1/2, z−1/2.