add.obigt {CHNOSZ}R Documentation

Functions to Work with the Thermodynamic Database

Description

Add or modify species in the thermodynamic database.

Usage

  add.obigt(file, species = NULL, force = TRUE, E.units = "cal")
  mod.obigt(...)
  today()

Arguments

file

character, path to a file

species

character, names of species to load from file

force

logical, force replacement of already existing species?

E.units

character, units of energy, cal or J

...

character or numeric, properties of species to modify in the thermodynamic database

Details

add.obigt is used to update the thermodynamic database (thermo$obigt) in the running session. The format (column names) of the specified file must be the same as the extdata/OBIGT/*.csv files provided with CHNOSZ.

file is first matched against the names of files in the extdata/OBIGT directory packaged with CHNOSZ. In this case, the filename suffixes are removed, so DEW_aq, organic_aq, and organic_cr are valid names. The function also accepts single matches with the state suffix dropped (DEW but not organic). If there are no matches to a system file, then file is interpreted as the path a user-supplied file.

If species is NULL (default), all species listed in the file are used. If species is given and matches the name(s) of species in the file, only those species are added to the database.

By default, species in the file replace any existing species having the same combination of name and state. Set force to FALSE to avoid replacing species that are present in (thermo$obigt).

Given the default setting of E.units, the function does not perform any unit conversions. If E.units is set to J, then the thermodynamic parameters are converted from units of Joules to calories, as used in the CHNOSZ database.

When adding species, there is no attempt made to keep the order of physical states in the database (aq-cr-liq-gas); the function simply adds new rows to the end of thermo$obigt. As a result, retrieving the properties of an added aqueous species using info requires an explicit state="aq" argument to that function if a species with the same name is present in one of the cr, liq or gas states.

mod.obigt changes one or more of the properties of species or adds species to the thermodynamic database. These changes are lost if you reload the database by calling data(thermo) or if you quit the R session without saving it. The name of the species to add or change must be supplied as the first argument of ... or as a named argument (named name). When adding new species, a chemical formula should be included along with the values of any of the thermodynamic properties. The formula is taken from the formula argument, or if that is missing, is taken to be the same as the name of the species. An error results if the formula is not valid (i.e. can not be parsed bymakeup). Additional arguments refer to the name of the property(s) to be updated and are matched to any part of compound column names in thermo$obigt, such as z or T in z.T. Unless state is specified as one of the properties, its value is taken from thermo$opt$state. When adding species, properties that are not specified become NA (except for state). The values provided should be in the units specifed in the documentation for the thermo data object, including any order-of-magnitude scaling factors.

today returns the current date in the format adopted for thermo$obigt (inherited from SUPCRT-format data files) e.g. 13.May.12 for May 13, 2012.

Value

The values returned (invisible-y) are the indices of the added and/or modified species.

References

Bazarkina, E. F., Zotov, A. V., and Akinfiev, N. N. (2010) Pressure-dependent stability of cadmium chloride complexes: Potentiometric measurements at 1-1000 bar and 25°C. Geology of Ore Deposits 52, 167–178. https://doi.org/10.1134/S1075701510020054

Sverjensky, D. A., Shock, E. L., and Helgeson, H. C. (1997) Prediction of the thermodynamic properties of aqueous metal complexes to 1000 °C and 5 kbar. Geochim. Cosmochim. Acta 61, 1359–1412. https://doi.org/10.1016/S0016-7037(97)00009-4

See Also

thermo, util.data, mod.buffer

Examples

## modify an existing species (example only)
ialanine <- mod.obigt("alanine", state="cr", G=0, H=0, S=0)
# we have made the values of G, H, and S inconsistent
# with the elemental composition of alanine, so the following 
# now produces a message about that
info(ialanine)
## add a species
iCl2O <- mod.obigt("Cl2O", G=20970)
info(iCl2O)
# add a species with a name that is different from the formula
mod.obigt("buckminsterfullerene", formula="C60", state="cr", date=today())
# retrieve the species data (thermodynamic properties in this toy example are NA)
info(info("C60"))
# reset database
data(OBIGT)

# using add.obigt():
# compare stepwise stability constants of cadmium chloride complexes
# using data from Sverjensky et al., 1997 and Bazarkina et al., 2010
Cdspecies <- c("Cd+2", "CdCl+", "CdCl2", "CdCl3-", "CdCl4-2")
P <- c(1, seq(25, 1000, 25))
SSH97 <- lapply(1:4, function(i) {
  subcrt(c(Cdspecies[i], "Cl-", Cdspecies[i+1]),
    c(-1, -1, 1), T=25, P=P)$out$logK
})
file <- system.file("extdata/thermo/BZA10.csv", package="CHNOSZ")
add.obigt(file)
BZA10 <- lapply(1:4, function(i) {
  subcrt(c(Cdspecies[i], "Cl-", Cdspecies[i+1]),
    c(-1, -1, 1), T=25, P=P)$out$logK
})
# reset default database
data(OBIGT)
matplot(P, do.call(cbind, SSH97), type="l")
matplot(P, do.call(cbind, BZA10), type="l", add=TRUE, lwd=2)
legend("topleft", legend=c("", "", "Sverjensky et al., 1997",
  "Bazarkina et al., 2010"), lwd=c(0, 0, 1, 2), bty="n")
# make reaction labels
y <- c(1.8, 0.2, -0.5, -1)
invisible(lapply(1:4, function(i) {
  text(800, y[i], describe.reaction(subcrt(c(Cdspecies[i], "Cl-",
    Cdspecies[i+1]), c(-1, -1, 1), T=25, P=1)$reaction))
}))

[Package CHNOSZ version 1.1.3 Index]