Abstract
APL computer programs for the thermodynamic calculation of devolatilization and solid-solid equilibria operate using stored values for the molar volume and entropy of solids, the free energies of H2O and CO2, and the free energies of formation for 110 geologically-important phases. P-T-X CO 2 calculations of devolatilization equilibria can be made at pressures from 0.2 through 10 kb, and temperatures from 200 through 1,000° C. P-T-X calculations of solid-solid equilibria may be accomplished at pressures to 30 kb and temperatures to 1,000° C. Calculations can be extrapolations from experimental points, or direct calculations from thermochemical data alone. Options are available in these programs to consider effects of: real vs. ideal gas mixing, thermal expansion and compressibility, solid solution, fluid pressure differing from solid pressure, and uncertainties in high-temperature entropies.
A collection of thermodynamic data programs accompanies the programs for calculating P-T-X CO 2 equilibria. Over a wide range of physical conditions, the data functions report free energies, entropies, fugacities of H2O and CO2, high temperature entropies of solids, and activities of components in H2O-CO2 mixtures.
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Abbreviations
- \(a_{{\text{H}}_{\text{2}} {\text{O}}} ,a_{{\text{CO}}_{\text{2}} }\) :
-
Activity of H2O and CO2
- Δ Gf :
-
Free energy of formation of a phase from elements
- Δ Gr :
-
Free energy change of reaction
- Δ G or :
-
Standard state free energy change of a reaction
- \(G_{{\text{H}}_{\text{2}} {\text{O}}} ,G_{{\text{CO}}_{\text{2}} }\) :
-
Free energies of pure H2O and CO2
- Δ H or :
-
Standard state enthalpy change for a reaction
- K:
-
Equilibrium constant
- R:
-
Gas constant
- Δ S or :
-
Standard state entropy change of reaction
- Δ S os :
-
Standard state entropy change of solids in a reaction
- Δ Vs o :
-
Standard state volume change of a reaction
- Δ Vs o :
-
Standard state volume change of solids in a reaction
- \(X_{{\text{H}}_{\text{2}} {\text{O}}} ,X_{{\text{CO}}_{\text{2}} }\) :
-
Mole fraction of H2O and CO2
- \(\gamma _{{\text{H}}_{\text{2}} {\text{O}}} ,\gamma _{{\text{CO}}_{\text{2}} }\) :
-
Activity coefficient of H2O and CO2
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Slaughter, J., Wall, V.J. & Kerrick, D.M. APL computer programs for thermodynamic calculations of equilibria in P-T-X CO 2 space. Contr. Mineral. and Petrol. 54, 157–171 (1976). https://doi.org/10.1007/BF00371004
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DOI: https://doi.org/10.1007/BF00371004