Fast electron diffraction tomography

A fast and fully automatic procedure for collecting electron diffraction tomography data is presented. In the case of a very stable goniometer it is demonstrated how, by variation of the tilting speed and the CCD detector parameters, it is possible to obtain fully automatic precession-assisted electron diffraction tomography data collections, rotation electron diffraction tomography data collections or new integrated electron diffraction tomography data collections, in which the missing wedge of the reciprocal space between the patterns is recorded by longer exposures during the crystal tilt. It is shown how automatic data collection of limited tilt range can be used to determine the unit-cell parameters, while data of larger tilt range are suitable to solve the crystal structure ab initio with direct methods. The crystal structure of monoclinic MgMoO₄ has been solved in this way as a test structure. In the case where the goniometer is not stable enough to guarantee a steady position of the crystal over large tilt ranges, an automatic method for tracking the crystal during continuous rotation of the sample is proposed.

Computing details

Program(s) used to solve structure: SIR2011 (Burla et al., 2011).

Magnesium Molybdate

Crystal data

MgMoO4	β = 105.900°
Mr = 184.24	V = 634.6 Å^3
Monoclinic, C2/m	Z = 8
a = 10.157 Å	Cell parameters from 1608 reflections
b = 9.246 Å	θ = 0.0–0.0°
c = 7.030 Å	T = 293 K

Data collection

711 independent reflections	k = →
711 reflections with F > 3.0 σ(F)	l = →
h = →

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

	x	y	z	Uiso*/Ueq
Mo1	0.0000	0.2534	0.5000	0.00746*
Mo2	−0.2712	0.0000	0.0953	0.00707*
Mg1	0.0000	0.8234	0.0000	0.00777*
Mg2	0.1986	0.0000	0.3593	0.00008*
O1	0.5387	0.6513	0.3036	0.00324*
O2	−0.8691	0.6518	0.0225	0.00953*
O3	−0.8658	0.3573	0.6113	0.01570*
O4	0.6393	0.5000	0.0383	0.00178*
O5	0.2003	0.0000	0.6318	0.00760*