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The structural phase transition accompanied by a Jahn-Teller switch has been studied over a range of H/D ratios in (NH4)2[Cu(H2O)6](SO4)2 (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. [ABSTRACT FROM AUTHOR]

In situ synchrotron powder diffraction has been used to probe the pressure-dependent structural properties of the magnetic molecular framework material Co(dca)2 [dca = dicyanamide or N(CN)2−]. An orthorhombic ( Pmnn) to monoclinic ( P21/ n) transformation to a high-pressure phase, namely γ-Co(dca)2, occurs at 1.1 GPa. Structural determination of γ-Co(dca)2 shows that the rutile-like topology of the pristine material is retained at high pressures, with the lower symmetry allowing a progression of volume-reducing structural distortions. γ-Co(dca)2 was stable at the maximum pressure measured of 4.2 GPa. Both phases were soft, with bulk moduli ( B0) for α-Co(dca)2 and γ-Co(dca)2 of 13.15 (18) and 9.0 (6) GPa, respectively. Modest uniaxial negative linear compressibility ( K) of the order of −4 TPa−1 was observed over the entire measured pressure range. [ABSTRACT FROM AUTHOR]

The structural phase transition accompanied by a Jahn-Teller switch has been studied over a range of H/D ratios in (NH4)2[Cu(H2O)6](SO4)2 (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. [ABSTRACT FROM AUTHOR]