A High-Pressure Investigation of the Synthetic Analogue of Chalcomenite, CuSeO3∙2H2O

Abstract

Synthetic chalcomenite-type cupric selenite CuSeO3∙2H2O has been studied at room temperature under compression up to pressures of 8 GPa by means of single-crystal X-ray diffraction, Raman spectroscopy, and density-functional theory. According to X-ray diffraction, the orthorhombic phase undergoes an isostructural phase transition at 4.0(5) GPa with the thermodynamic character being first-order. This conclusion is supported by Raman spectroscopy studies that have detected the phase transition at 4.5(2) GPa and by the first-principles computing simulations. The structure solution at different pressures has provided information on the change with pressure of unit–cell parameters as well as on the bond and polyhedral compressibility. A Birch–Murnaghan equation of state has been fitted to the unit–cell volume data. We found that chalcomenite is highly compressible with a bulk modulus of 42–49 GPa. The possible mechanism driving changes in the crystal structure is discussed, being the behavior of CuSeO3∙2H2O mainly dominated by the large compressibility of the coordination polyhedron of Cu. On top of that, an assignation of Raman modes is proposed based upon density-functional theory and the pressure dependence of Raman modes discussed. Finally, the pressure dependence of phonon frequencies experimentally determined is also reported.

The Phase Transition and Dehydration in Epsomite under High Temperature and High Pressure

“…We think that this is possibly related to the distortion of the sulfate tetrahedra and the strengthening of the hydrogen bonding. A recent work by Gonzalez-Platas et al revealed that the chalcomenite underwent an isostructural phase transition at around ~4.0 GPa, which is very close to the transition point of epsomite that was revealed in this study (~5.1 GPa) [20]. The similarities between the transition pressures are closely associated with their crystal structure, because both of them have an orthorhombic structure with the same space group of P212121.…”

First-Order Isostructural Phase Transition Induced by High Pressure in Fe(IO3)3

“…3 On the other hand, numerous iodates are fascinating because they have IO 3 units with lone-pair orbitals, 4 which give materials particular characteristics. 5 High-pressure (HP) research is known to be an efficient tool to determine the characteristics of materials. 6 In general, HP reduces the interatomic distances in materials in a controlled manner, which results in significant changes of the physical and chemical characteristics.…”

Raman spectroscopy and X‐ray diffraction of pressure‐induced reversible structure change in K2OsO2(OH)4

“…By fitting to the third‐order Birch‐Murnaghan EOS, the bulk modulus of K 2 OsO 2 (OH) 4 is B 0 = 46(1) GPa and = 4. The bulk modulus of K 2 OsO 2 (OH) 4 is similar to CuSeO 3 ·2H 2 O (42–49 GPa), 6 which means a similar compressibility. Considering hydrated oxides are more compressible than their dehydrated counterparts 25 ; our study on K 2 OsO 2 (OH) 4 is putting a constraint on the bulk modulus of K 2 OsO 4 , which has not been studies.…”

“…Possible application as catalyst for the asymmetric dihydroxylation of olefins has been proposed 5 . Furthermore, high pressure could lead to pressure‐induced phase transitions in many similar hydrated minerals like FeSO4·H 2 O and CuSeO 3 ·2H 2 O 6 . The structural stability and vibrational properties of K 2 OsO 2 (OH) 4 under high pressure have not been yet fully discussed, which deserves further investigation.…”