Abstract
The crystal structure of the high-pressure phase of potassium hydrogen carbonate, here termed KHCO3 form III, has been solved using single-crystal X-ray diffraction techniques. It adopts triclinic P1̅ symmetry and is formed on direct compression of the monoclinic ambient-pressure phase (kalicinite, form I) via a first-order phase transition at 3.2 GPa (ΔV/V ~4%). We have also used time-of-fight high-pressure neutron powder-diffraction to determine the structural changes in KDCO3 of the form I and III polymorphs to 8.3 GPa. This study indicates that the transition appears to be in response to pronounced displacements of the K+ cations and the cooperative tilting of the (DCO3-)2 dimers. The O···O hydrogen bond distance shows a monotonic compression over the entire pressure range studied with no obvious discontinuity at the phase transition. However, the O-D···O bond angle appears to exhibit an abrupt ~4° decrease across the I.III phase transition with a concomitant change in its pressure dependence. Birch Murnaghan fits to the equation of state data above and below the transition indicate that form III [B0 = 26.5(2.8) GPa, B’ = 5.2(6)] is marginally less compressible than form I [B0 = 22.7(8) GPa, B’ = 4.1(5)].
© 2015 by Walter de Gruyter Berlin/Boston
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Articles in the same Issue
- Experimental evidence of sixfold oxygen coordination for phosphorus
- Dehydration of Ca-montmorillonite at the crystal scale. Part I: Structure evolution
- Dehydration of Ca-montmorillonite at the crystal scale. Part 2. Mechanisms and kinetics
- The high-pressure crystal structure of potassium hydrogen carbonate (KHCO3)
- Effect of Al3+ and H+ on the elastic properties of stishovite
- Investigation of synthetic Mg1.3V1.7O4 spinel with MgO inclusions: Case study of a spinel with an apparently occupied interstitial site
- Thermal expansion of deuterated hopeite, Zn3(PO4)2·4D2O
- Compression, thermal expansion, structure, and instability of CaIrO3, the structure model of MgSiO3 post-perovskite
- Crystal chemical relationships in the tourmaline group: Structural constraints on chemical variability
- The energetics of hematite dissolution in iron-oxide-rich melts: In situ high-temperature calorimetric studies
- A simple model of oscillatory zoning in magmatic plagioclase: Development of an isothermal undercooling model
- TEM investigation of Ca-rich plagioclase: Structural β uctuations related to the I1-P1 phase transition
- Crystal-chemistry of Ni in marine ferromanganese crusts and nodules
- Effect of structural transitions on properties of high-pressure silicate melts: 27Al NMR, glass densities, and melt viscosities
- Material conversion from paper-sludge ash in NaOH, KOH, and LiOH solutions
- High-pressure phase relations and crystal chemistry of calcium ferrite-type solid solutions in the system MgAl2O4-Mg2SiO4
- Origin of atoll garnets in eclogites and implications for the redistribution of trace elements during slab exhumation in a continental subduction zone
- Determination of the refractive index of particles in the clay and sub-micrometer size range
- Crystal chemistry of synthetic Ca2Al3Si3O12OH–Sr2Al3Si3O12OH solid-solution series of zoisite and clinozoisite
- Thermal infrared spectroscopy and modeling of experimentally shocked basalts
- P-V and T-V Equations of State of natural biotite: An in-situ high-pressure and high-temperature powder diffraction study, combined with Mössbauer spectroscopy
- Cation ordering in MgTi2O5 (karrooite): Probing temperature dependent effects with neutrons
- An order-disorder model for omphacitic pyroxenes in the system jadeite-diopsidehedenbergite- acmite, with applications to eclogitic rocks
- The high-pressure structural configurations of Ca0.2Sr0.8Al2Si2O8 feldspar: The I1̅-I2/c and I2/c-P21/c phase transitions
- Mechanisms of diamond oxidation and their bearing on the fluid composition in kimberlite magmas
- Brittle fracturing and fracture healing of zircon: An integrated cathodoluminescence, EBSD, U-Th-Pb, and REE study
- Galaxite, MnAl2O4, a spectroscopic standard for tetrahedrally coordinated Mn2+ in oxygen-based mineral structures
- Magmatic paragonite in trondhjemites from the Sierra del Convento mélange, Cuba
- Valence state partitioning of Cr and V between pyroxene-melt: Estimates of oxygen fugacity for martian basalt QUE 94201
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