High-pressure states in condensed matter: I. High-pressure behavior of the iron-sulfur system with applications to the earth's core. II. Empirical equation of state for organic compounds at high pressure.

摘要

Part I. An equation of state for liquid iron is presented, based on experimental data published in the literature and advanced theoretical models. This is important to models of the earth's interior and has never been done previously. In this equation of state, which is anchored at the normal melting point of 1811 K at 1 bar, it is found that the density and bulk modulus at these conditions are 7037 kg/m{dollar}sp3{dollar} and 110 GPa, respectively, and that the pressure derivatives of the bulk modulus are K{dollar}spprime{dollar} = 4.531 and K{dollar}sp{lcub}primeprime{rcub}{dollar} = {dollar}-{dollar}.0337 GPa{dollar}sp{lcub}-1{rcub}{dollar}. Comparison of this equation of state with PREM shows that the density deficit of the outer core depends strongly on one's assumption of the temperatures in the core, but that the inner core is almost certainly at a lower density than pure Fe. This inner core density deficit may be due to the inner core containing some fraction of a light element or also containing some liquid. The upper limit to the possible liquid content of the inner core is 50% by volume.; New experimental shock melting data are also presented for FeS and FeS{dollar}sb2{dollar}. It is found that FeS melt sat significantly lower temperatures than FeS{dollar}sb2{dollar} at high pressures. Application of an associated solution model for the FeS system, based on the behavior of analog intermetallic compounds, allows us to obtain phase diagrams for the Fe-S system. The results imply that FeS begins to undergo peritectic decomposition at about 100 GPa and has disappeared as a stable phase coexisting with liquid at pressures greater than about 170 GPa. A model of the core is suggested in which the outer core contains a slurry. Contrary to previous authors' assertions, the presence of a slurry will not hinder convection.; Part II. An empirical equation of state for organic liquids is suggested, based on previous assertions that the properties of organic compounds can be modelled as additive functions of molecular structure. We find that experimental data can be accurately modelled in this way and develop an expression for the pressure derivatives of the bulk modulus, based on the temperature dependence of the sound speed. Is is also found that this temperature dependence is an additive function of molecular structure.