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S. Danielsson

Bio: S. Danielsson is an academic researcher. The author has contributed to research in topics: Quartz & Atmospheric temperature range. The author has an hindex of 1, co-authored 1 publications receiving 8 citations.

Papers
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TL;DR: In this article, an automatic low-temperature apparatus to be used in single-crystal diffractometry is given, in which the crystal is cooled by a stream of nitrogen gas.
Abstract: A detailed description of an automatic low-temperature apparatus to be used in single-crystal diffractometry is given. The crystal is cooled by a stream of nitrogen gas. Prevention of ice formation on the crystal is achieved by heating the outer parts of the gas stream by a conical metal device. The unit-cell dimensions of α-quartz have been determined in the temperature range 86–298 K with this apparatus on a four-circle diffractometer of type CAD-4.

8 citations


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Journal ArticleDOI
01 Sep 2004
TL;DR: In this paper, the Gibbs free energy (GFE) formulation of the P-T partition function in statistical thermodynamics is used to derive semi-empirical formulations of the GFE for minerals and fluids.
Abstract: The P–T partition function in statistical thermodynamics can be used to derive semi-empirical formulations of the Gibbs free energy G for minerals and fluids Parameterization of these equations includes simultaneous regression of experimental heat capacity and molar volume data, allowing fitting, appraisal and optimization of various data sources, as required in the construction of internally consistent petrological data bases This approach can also be extended to minerals with λ-transitions and to fluids by considering the Gibbs free energy as a function of pressure P, temperature T and an ordering parameter Xα, so that accurate modelled representation and extrapolation of the thermodynamic properties of large numbers of petrologically significant minerals and coexisting fluids can be attained The ordering parameter is chosen to denote the equilibrium mole fraction (thermodynamic probability) of ordered clusters (structural units) in a substance when G(T,P, Xα)=min The procedure is tested on existing experimental data for the system MgO–SiO2–H2O The proposed Gibbs free energy formulation permits thermodynamic properties of minerals, fluids and phase equilibria to be described and extrapolated over a wide range of pressure (0–800 kbar) and temperature (20–3000 K), thus allowing effective use in thermodynamic data bases of petrological interest

39 citations

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TL;DR: In this paper, the isotope signatures in natural systems require knowledge of the equilibrium isotope fractionation between Si-bearing solids and the dominant Sibearing aqueous species.

31 citations

Journal ArticleDOI
TL;DR: In this paper, the crystal structure of hexagonal LiIO3 has been determined by neutron and x-ray diffraction at ten temperatures from 20 to 500 K, with the final agreement factors falling between 0.023 and 0.050.
Abstract: The crystal structure of hexagonal α‐LiIO3 has been determined by neutron and x‐ray diffraction at ten temperatures from 20 to 500 K. Four sets (1248 to 1622 reflections per set) of neutron data at λ=1.0467 A were measured at the Brookhaven High Flux Beam Reactor at 20, 100, 200, and 295 K. The integrated intensities of a further 13 data sets (1706 to 2963 reflections per set) were measured using MoKα radiation on a CAD‐4 x‐ray diffractometer. The structure at each temperature was refined by least squares in space group P63. The final agreement factors fell between 0.023 and 0.050. The unit cell dimensions at 295 K are a=5.481 27(6), c=5.171 65(4) A, with nonlinear thermal expansions. The principal change in structure with temperature is in the atomic positions of Li and O relative to I: The positions are given by O(z)T=−0.8435(3) A+62(4)×10−9 T2 A K−2 and Li(z)T=0.3808(10) A+167 (18)×10−9 T2 A K−2. The iodate ion has a constant I–O bond length of 1.8081(4) A, but the O–I–O angle increases from 99.97(2)° ...

28 citations

Journal ArticleDOI
TL;DR: In this paper, an equation of state has been developed for quartz, a substance with a lambda-type phase transition, which has the properties of the Murnaghan equation in the normal region and reflects the fundamental behavior of thermodynamic functions in the anomalous region.
Abstract: An equation of state has been developed for quartz, a substance with a lambda-type phase transition. It has the properties of the Murnaghan equation of state in the normal region and reflects the fundamental behavior of thermodynamic functions in the anomalous region. The term jT/(i-T)1/2 has been introduced in the temperature dependent equations of isobaric heat capacity and the volume coefficient of thermal expansion, where i and j are fitting coefficients. The i coefficient is numerically close to the temperature of the phase transition Tc and is usually in the 0.1<|i-Tc|<20 K interval. The range of applicability of the Murnaghan equation is delineated in the PT stability field of quartz. In the lambda range, the derivative of thermal expansion with respect to temperature is pressure dependent according to rules that allow integration of the thermal expansion and molar volume for calculation of the change in thermodynamic functions from room pressure to any given pressure. Available phase equilibria and thermochemical data have been used with the proposed equation of state to calculate the standard thermodynamic properties for coesite and the SiO2 phase diagram including alpha quartz, beta quartz, and coesite.

21 citations

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TL;DR: In this paper, the EPR spectrum of the trapped-hole species [AlO4]0 in single-crystal α-quartz at ca. 25 K was measured and it was shown that the unpaired electron is located primarily at an oxygen anion adjacent to the substitutional aluminum impurity cation.

16 citations