add diffusion coefficients

[Mr.white]

Ca+2 = Ca+2
   -gamma   5.0   0.1650
   -dw   0.793e-9  97  3.4  24.6
   -Vm  -0.3456  -7.252  6.149  -2.479  1.239  5  1.60  -57.1  -6.12e-3
Mg+2 = Mg+2
   -gamma   5.5   0.20
   -dw   0.705e-9  111  2.4  13.7
   -Vm  -1.410  -8.6  11.13  -2.39  1.332  5.5  1.29  -32.9  -5.86e-3
I want to understand how to add diffusion coefficients for methane, ethane, and propane in the database. Currently, when performing diffusion simulations, only the inert form of C1 is kept in the SOLUTION_SPECIES section as C1 = C1 -log_k 0. However, I want to know the format for adding diffusion coefficients. I have listed two substances from the database; does "dw" represent the diffusion coefficient? What do the numbers following "dw" represent?

[dlparkhurst]

The latest version of PHREEQC is 3.8.0. The SOLUTION_SPECIES documentation describes the parameters and gives the equations.

For the batch phreeqc, the download is found at https://github.com/usgs-coupled/phreeqc3/releases. After installing, the documentation file is directory C:\Program Files\USGS\phreeqc-3.8.0-16920-x64\doc\phreeqc3.chm.

For PhreeqcI, the download is found at https://github.com/usgs-coupled/phreeqci/releases. You can find documentation by clicking Help in the top bar of PhreeqcI. The documentation file is also found as C:\Program Files (x86)\USGS\Phreeqc Interactive 3.8.0-16912\doc\phreeqci.chm.

Sometimes, .chm files cannot be opened completely, and it is necessary to unblock the file. Using a PowerShell prompt, the command is Unblock-File.