We present in situ observations of hydrocarbon formation via carbonate reduction at upper mantle pressures and temperatures. Methane was formed from FeO, CaCO3-calcite, and water at pressures between 5 and 11 GPa and temperatures ranging from 500°C to 1,500°C. The results are shown to be consistent with multiphase thermodynamic calculations based on the statistical mechanics of soft particle mixtures. The study demonstrates the existence of abiogenic pathways for the formation of hydrocarbons in the Earth's interior and suggests that the hydrocarbon budget of the bulk Earth may be larger than conventionally assumed.

The complete series of phenylchalcogenolate derivatives of permethylzirconocene Cp*2Zr(EPh)2 (Cp* = z/5-C;-Mes; E = O, S, Se, Te) has been prepared by the reactions of Cp*2Zr(CO)2 with PhOH and Ph2E2 (E = S, Se, Te). The molecular structures of all of the derivatives Cp*2Zr(EPh)2 have been determined by X-ray diffraction, thereby providing evidence that the nature of the bonding varies as a function of the chalcogen. Specifically, the structure of the phenoxo derivative is notably distinct from those of its heavier congeners. For example, whereas the Zr-S, Zr-Se, and Zr-Te bond lengths are comparable to the sum of their respective covalent radii, the Zr-O bond length is significantly shorter than the sum of the covalent radii, as would be anticipated due to an increased ionic contribution to the bonding. In addition, the Zr-O-C bond angle [172.7(2)°] in Cp*2-Zr(OPh)2 is effectively linear, whereas the Zr-E-C bond angles for the heavier congeners are significantly bent [113°-119°]. Comparison of the structure of Cp*2Zr(OPh)2 with that of the less substituted zirconocene derivative Cp2Zr(OPh)2, which possesses a bent Zr-O-C moiety [147(1)°], suggests that the linearity of Cp*2Zr- (OPh)2 may be attributed to steric factors. Thus, short M-OR bond lengths and linear M-O-R angles are not necessarily a consequence of strong -djr lone pair donation from oxygen to the metal. Cp*2Zr(OPh)2 is monoclinic: C2Jc (No. 15), a = 11.049( 2) k,b= 15.445(3) A, c = 17.141(3) Á, ß = 104.24(1)°, and Z = 4. Cp*2Zr(SPh)2 is monoclinic: C2/c (No. 15), a = 14.444(4) k,b= 11.449(2) A, c = 18.262(3) Á, ß = 103.39-(2)°, and Z = 4. Cp*2Zr(SePh)2 is hexagonal: P6\ (No. 169), a = 12.903(2) A, c = 31.923(6) A, and Z = 6. Cp*2Zr(TePh)2 is monoclinic: P2,/c (No. 14), a = 16.917(3) k,b = 25.326(6) A, c = 15.234(4) A, ß = 107.95-(2)°, and Z = 8. Cp2Zr(OPh)2 is orthorhombic: Aba2 (No. 41), a = 8.274(3) k,b= 19.843(9) A, c = 11.586-(8) A, and Z = 4.

Articles you may be interested inAnalysis of the validity of perturbation density functional theory: Based on extensive simulation for simple fluid at supercritical and subcritical temperature under various external potentials J. Chem. Phys. 122, 064503 (2005); 10.1063/1.1843814 Comparison of polarizable and nonpolarizable models of hydrogen fluoride in liquid and supercritical states: A Monte Carlo simulation study Effective Hamiltonian analysis of fluid criticality and application to the square-well fluidThe exponential-6 potential model is widely used in fluid equation of state studies. We have developed an accurate and efficient complete equation of state for the exponential-6 fluid based on HMSA integral equation theory and Monte Carlo calculations. Our equation of state has average fractional error of 0.2% in pV/Nk B T and 0.3% in the excess energy U ex /Nk B T. This is a substantial improvement in accuracy over perturbation methods, which are typically used in treatments of dense fluid equations of state. We have applied our equation of state to the problem of dense supercritical N 2 . We find that we are able to accurately reproduce a wide range of material properties with our model, over a range 0.01р Pр100 GPa and 298рTр15 000 K.

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