Defect contributions to the heat capacities and stabilities of some chain, ring, and sheet silicates, with implications for mantle minerals

Molar heat capacities of 2,3,6-trimethylpyridine, 2,4,6-trimethylpyridine and 3-methoxypropionitrile in the liquid state were measured at the constant atmospheric pressure in the temperature interval of 300.60 to 328.35 K. The static type of adiabatic calorimeter was used for the measurements.

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Heat capacities and enthalpies of fusion and transformation for solvates of some salts with dimethyl sulfoxide and dimethylformamide

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19883072 ◽

1988 ◽

Vol 53 (12) ◽

pp. 3072-3079

Author(s):

Mojmír Skokánek ◽

Ivo Sláma

Keyword(s):

Heat Capacity ◽

Phase Transformation ◽

Phase Transformations ◽

Dimethyl Sulfoxide ◽

Liquidus Temperature ◽

Molar Heat Capacity ◽

Solid Phase ◽

Zinc Nitrate ◽

Heat Capacities ◽

Liquid Phases

Molar heat capacities and molar enthalpies of fusion of the solvates Zn(NO3)2 . 2·24 DMSO, Zn(NO3)2 . 8·11 DMSO, Zn(NO3)2 . 6 DMSO, NaNO3 . 2·85 DMSO, and AgNO3 . DMF, where DMSO is dimethyl sulfoxide and DMF is dimethylformamide, have been determined over the temperature range 240 to 400 K. Endothermic peaks found for the zinc nitrate solvates below the liquidus temperature have been ascribed to solid phase transformations. The molar enthalpies of the solid phase transformations are close to 5 kJ mol-1 for all zinc nitrate solvates investigated. The dependence of the molar heat capacity on the temperature outside the phase transformation region can be described by a linear equation for both the solid and liquid phases.

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Diamond formation in an electric field under deep Earth conditions

Science Advances ◽

10.1126/sciadv.abb4644 ◽

2021 ◽

Vol 7 (4) ◽

pp. eabb4644

Author(s):

Yuri N. Palyanov ◽

Yuri M. Borzdov ◽

Alexander G. Sokol ◽

Yuliya V. Bataleva ◽

Igor N. Kupriyanov ◽

...

Keyword(s):

Electric Fields ◽

Lithospheric Mantle ◽

Isotope Fractionation ◽

Diamond Formation ◽

Mantle Minerals ◽

Electrochemical Processes ◽

Mantle Mineral ◽

Deep Earth ◽

Diamond Crystallization ◽

Global Carbon

Most natural diamonds are formed in Earth’s lithospheric mantle; however, the exact mechanisms behind their genesis remain debated. Given the occurrence of electrochemical processes in Earth’s mantle and the high electrical conductivity of mantle melts and fluids, we have developed a model whereby localized electric fields play a central role in diamond formation. Here, we experimentally demonstrate a diamond crystallization mechanism that operates under lithospheric mantle pressure-temperature conditions (6.3 and 7.5 gigapascals; 1300° to 1600°C) through the action of an electric potential applied across carbonate or carbonate-silicate melts. In this process, the carbonate-rich melt acts as both the carbon source and the crystallization medium for diamond, which forms in assemblage with mantle minerals near the cathode. Our results clearly demonstrate that electric fields should be considered a key additional factor influencing diamond crystallization, mantle mineral–forming processes, carbon isotope fractionation, and the global carbon cycle.

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