文摘
The structural phase transition accompanied by a Jahn–Teller switch has been studied over a range of H/D ratios in (NH<sub>4sub>)<sub>2sub>[Cu(H<sub>2sub>O)<sub>6sub>](SO<sub>4sub>)<sub>2sub> (ACTS). In particular, single-crystal neutron diffraction investigations of crystals with deuteration in the range 50 to 82% are shown to be consistent with previous electron paramagnetic resonance (EPR) experiments exhibiting a phase boundary at 50% deuteration under ambient pressure. Polycrystalline samples show that the two phases can co-exist. In addition, single-crystal neutron and polycrystalline X-ray diffraction pressure experiments show a shift to lower pressure at 60% deuteration versus previous measurements at 100% deuteration.