Electron-density distribution in cubic SrTiO₃: a comparative γ-ray diffraction study

The electron density and atomic displacements in the perovskite SrTiO₃ have been studied using extensive and accurate γ-ray diffraction data (λ = 0.0392 Å) at room temperature. The six strongest low-order structure factors have been determined under extinction-free conditions. Gram–Charlier series expansion of the thermal parameters have revealed no evidence for anharmonicity. The population of the 3d subshell on Ti is found to be close to zero, in agreement with the observed magnetic behaviour. The electronic properties at the bond critical points indicate ionic Ti—O and Sr—O interactions of different strengths, which is corroborated by the net charges of the atomic basins [q(Sr) = 1.18 |e|, q(Ti) = 3.10 |e|, q(O) = −1.42 |e|]. A critical comparison is made with earlier experimental results from laboratory X-ray, synchrotron X-ray, electron and neutron diffraction studies. Agreement and discrepancies are identified and resolved.

Computing details

Data reduction: xtal_ADDREF_SORTRF; program(s) used to solve structure: Xtal; program(s) used to refine structure: Xtal; molecular graphics: Xtal; software used to prepare material for publication: xtal_CIFIO.

(I)

Crystal data

SrTiO3	V = 59.56 Å^3
Cubic, p_m_3_m	Dx = 5.116 Mg m^−3
Hall symbol: -p_4_2_3	Gamma-radiation (316.5 KeV)
a = 3.9053 Å	T = 293 K

Data collection

776 measured reflections	θmax = 3.9°, θmin = 0.3°
174 independent reflections	h = 0→12
174 reflections with refl_observed_if_F^2_ > _.000_σ(F^2)	k = −8→12
Rint = 0.012	l = −2→8

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

	x	y	z	Uiso*/Ueq
ti	0.50000	0.50000	0.50000	0.00395*
sr	0.00000	0.00000	0.00000	0.00578*
o	0.50000	0.50000	0.00000	0.00732

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
o	0.00932	0.00932	0.00333	0.00000	0.00000	0.00000