The structure of nano-twinned rhombohedral YCuO_2.66 solved by electron crystallography

In the search for frustrated spin interactions, a YCuO_2.66 phase has been synthesized by a treatment under oxygen pressure of YCuO_2.5. X-ray powder diffraction and electron diffraction studies have been conducted. Electron diffraction shows that the sample is twinned on a 10 nm scale. Precession electron diffraction data obtained from a twinned crystal was treated in order to obtain intensities corresponding to only one of the orientations of the twins. From this data a structure solution was obtained where, as in YCuO_2.5, the Cu atoms form triangular planes. The Cu atoms are linked in two dimensions by oxygen atoms in the present structure whereas in YCuO_2.5 they are only linked in one-dimensional chains.

Computing details

(YCuO26)

Crystal data

Y18Cu18O48	c = 33.6000 Å
Mr = 3512.09	α = 90°
Rhombohedral, R3c	γ = 120°
Hall symbol: R_3_-2"c	V = 1129.4 Å^3
a = 6.2300 Å

Data collection

h = →	l = →
k = →

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

	x	y	z	Uiso*/Ueq
Y1	0.0000	0.0000	0.1573	0.00127*
Y2	−0.3333	0.3333	0.1579	0.00127*
Y3	0.3333	0.6667	0.1485	0.01098*
CU1	0.0054	0.3074	0.0824	0.00127*
O1	−0.0324	0.3093	0.1325	0.00849*
O2	0.0000	0.0000	0.0500	0.16397*
O3	0.0000	0.0000	0.2301	0.05831*
O4	0.2256	0.3513	0.1946	0.00127*

Bond lengths (Å)

Y1—O3	2.4441	Y3—O4^ii	2.3202
Y3—O2^i	2.2901

Symmetry codes: (i) −x+y+1/3, y+2/3, z−1; (ii) −y+1, x−y+1, z.