Calculate thermodynamic properties using the revised Helgeson-Kirkham-Flowers (HKF) equations of state for aqueous species, or using a generic heat capacity equation for crystalline, gas, and liquid species.
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character, name(s) of properties to calculate
numeric, temperature(s) at which to calculate properties (K)
numeric, pressure(s) at which to calculate properties (bar)
dataframe, species parameters as one or more rows from
character, which contributions to consider in the revised HKF equations equations of state: (
character, properties to calculate for water
The equations of state permit the calculation of the standard molal properties of species as a function of temperature and pressure.
property argument is required and refers to one or more of G, H, S, Cp and V, and for aqueous species only, kT and E.
The units of these properties are the first ones shown in the description for
The names of the properties are matched without regard to case.
hkf implements the revised HKF equations of state (Helgeson et al., 1981; Tanger and Helgeson, 1988; Shock and Helgeson, 1988).
The equations-of-state parameters are
Z; the units of these parameters are as indicated for
thermo$obigt, without the order of magnitude multipliers.
Note that the equation-of-state parameter
Z (appearing in the g-function for the temperature derivatives of the omega parameter; Shock et al., 1992) is taken from
thermo$obigt and not from the
makeup of the species.
H2O.props is an optional argument that lists the properties of water that should be returned; it is used by
subcrt so that the time-consuming water calculations are only performed once.
The temperature and pressure derivatives of the
omega parameter for charged species (where
Z != 0, but not for the aqueous proton, H+) are calculated using the g- and f-functions described by Shock et al., 1992 and Johnson et al., 1992.
This option is turned off when the IAPWS-95 equations are activated (see
The parameters in the
cgl equations of state for crystalline, gas and liquid species (except liquid water) include
The terms denoted by
c correspond to the Maier-Kelley equation for heat capacity (Maier and Kelley, 1932); the additional terms are useful for representing heat capacities of minerals (Robie and Hemingway, 1995) and gaseous or liquid organic species (Helgeson et al., 1998).
The standard molal volumes (V) of species in these calculations are taken to be independent of temperature and pressure.
cgl, if at least one equations-of-state parameter for a species is provided, any NA values of the other parameters are reset to zero.
If all equations-of-state parameters are NA, but values of Cp and/or V are available, those values are used in the integration of G, H and S as a function of temperature.
P arguments should all be the same length; the functions perform no argument validating.
A list of length equal to the number of species (i.e., number rows of
Each element of the list contains a dataframe, each column of which corresponds to one of the specified properties; the number of rows is equal to the number of pressure-temperature points.
hkf, the output is a list consisting of the above-described object (named aq) and a data frame of the calculated properties of water (named H2O).
The temperature and pressure range of validity of the revised HKF equations of state for aqueous species corresponds to the stability region of liquid water or the supercritical fluid at conditions between 0 to 1000 °C and 1 to 5000 bar (Tanger and Helgeson, 1988; Shock and Helgeson, 1988).
hkf function does not check these limits and will compute properties as long as the requisite electrostatic properties of water are available. There are conceptually no temperature limits (other than 0 Kelvin) for the validity of the
cgl equations of state.
However, the actual working upper temperature limits correspond to the temperatures of phase transitions of minerals or to those temperatures beyond which extrapolations from experimental data become highly uncertain.
These temperature limits are stored in the thermodynamic database for some minerals, but
cgl ignores them; however,
subcrt warns if they are exceeded.
Helgeson, H. C., Kirkham, D. H. and Flowers, G. C. (1981) Theoretical prediction of the thermodynamic behavior of aqueous electrolytes at high pressures and temperatures. IV. Calculation of activity coefficients, osmotic coefficients, and apparent molal and standard and relative partial molal properties to 600°C and 5 Kb. Am. J. Sci. 281, 1249–1516. http://www.ajsonline.org/cgi/content/abstract/281/10/1249
Helgeson, H. C., Owens, C. E., Knox, A. M. and Richard, L. (1998) Calculation of the standard molal thermodynamic properties of crystalline, liquid, and gas organic molecules at high temperatures and pressures. Geochim. Cosmochim. Acta 62, 985–1081. https://doi.org/10.1016/S0016-7037(97)00219-6
Maier, C. G. and Kelley, K. K. (1932) An equation for the representation of high-temperature heat content data. J. Am. Chem. Soc. 54, 3243–3246. https://doi.org/10.1021/ja01347a029
Robie, R. A. and Hemingway, B. S. (1995) Thermodynamic Properties of Minerals and Related Substances at 298.15 K and 1 Bar (10^5 Pascals) Pressure and at Higher Temperatures. U. S. Geol. Surv., Bull. 2131, 461 p. http://www.worldcat.org/oclc/32590140
Shock, E. L. and Helgeson, H. C. (1988) Calculation of the thermodynamic and transport properties of aqueous species at high pressures and temperatures: Correlation algorithms for ionic species and equation of state predictions to 5 kb and 1000°C. Geochim. Cosmochim. Acta 52, 2009–2036. https://doi.org/10.1016/0016-7037(88)90181-0
Shock, E. L., Oelkers, E. H., Johnson, J. W., Sverjensky, D. A. and Helgeson, H. C. (1992) Calculation of the thermodynamic properties of aqueous species at high pressures and temperatures: Effective electrostatic radii, dissociation constants and standard partial molal properties to 1000 °C and 5 kbar. J. Chem. Soc. Faraday Trans. 88, 803–826. https://doi.org/10.1039/FT9928800803
Tanger, J. C. IV and Helgeson, H. C. (1988) Calculation of the thermodynamic and transport properties of aqueous species at high pressures and temperatures: Revised equations of state for the standard partial molal properties of ions and electrolytes. Am. J. Sci. 288, 19–98. http://www.ajsonline.org/cgi/content/abstract/288/1/19
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## aqueous species CH4aq <- info(info("methane", "aq")) hkf(property = "Cp", parameters = CH4aq) # the non-solvation heat capacity hkf(property = "Cp", parameters = CH4aq, contrib = "n") # at different temperature and pressure hkf(property = "Cp", parameters = CH4aq, T = c(373.15,473.15), P = 1000) ## crystalline, gas, liquid species CH4gas <- info(info("methane", "gas")) cgl(property = "Cp", parameters = CH4gas) # melting and vaporization of n-octane C8H18par <- info(info(rep("n-octane", 3), c("cr", "liq", "gas"))) myT <- seq(200, 420, 10) DG0f <- cgl(property = "G", parameters = C8H18par, T = myT, P = 1) cbind(T = myT, which.pmax(DG0f, pmin = TRUE)) # 1 = cr, 2 = liq, 3 = gas # compare that result with the tabulated transition temperatures print(C8H18par)
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