Single-crystal neutron diffraction in diamond anvil cells with hot neutrons

Abstract

It is demonstrated that it is possible to perform single-crystal measurements in diamond anvil cells (DACs) with a monochromatic beam at modern hot neutron sources that offer the benefit of short neutron wavelengths with high fluxes. A piston-cylinder DAC with conical Boehler-Almax diamonds that allows for a wide accessibility of the reciprocal space has been developed. The diffraction data collected in this cell using hot neutrons are of very good quality and can be used for a full and reliable structure refinement.

Combined X-ray and neutron single-crystal diffraction in diamond anvil cells

“…A comparison of the atomic coordinates from the present neutron data with those obtained previously (Grzechnik et al, 2018) shows that they agree very well within their estimated standard deviations (ESDs) ( Table 4). The interatomic distances are also identical within their ESDs to those from our panoramic cell (Table 5).…”

“…An approximately prismatic crystal of MnFe 4 Si 3 (about 0.4 Â 0.45 Â 0.6 mm) was loaded into memDAC together with a ruby chip. The size of the crystal is only slightly larger than the minimal size for crystals that can currently be measured at HEiDi before all the upgrades of the beamline are finished (Grzechnik et al, 2018). The diameter of the diamond culets was 1.5 mm.…”

“…Owing to the development of radiation sources and areasensitive detectors, single-crystal X-ray diffraction in a diamond anvil cell (DAC) can now be performed on very small samples (<10 À7 mm 3 ) with complex crystal structures up to megabar (1 Mbar = 100 GPa) pressures (Merlini & Hanfland, 2013). On the other hand, only two single-crystal neutron diffraction studies in a DAC have been reported, with complete structural refinements at 0.25 GPa (Binns et al, 2016) and 1.0 GPa (Grzechnik et al, 2018). The reason for this is that even at the most advanced neutron facilities it is difficult to study crystals with volumes below 1 mm 3 since the highest neutron fluxes are several orders of magnitude smaller than the photon fluxes at synchrotron sources.…”

“…For our high-pressure work at HEiDi, we constructed a panoramic DAC with a wide access to reciprocal space (Grzechnik et al, 2018). The data measured using this cell have a completeness of 76% ( full = 39.34 , = 1.17 Å ) and are of excellent quality, as demonstrated by a full structure refinement with standard tools in high-pressure crystallography (Friese et al, 2013;Petricek et al, 2014).…”

“…For our combined benchmark X-ray and neutron measurements, we chose a crystal of MnFe 4 Si 3 that has already been investigated in our earlier high-pressure neutron singlecrystal diffraction study (Grzechnik et al, 2018). The structure of this compound is well known and was determined at ambient conditions using joint X-ray and neutron data (Hering et al, 2015).…”