CAMP: UNIFAC Activity Coefficients

The UNIFAC activity coefficient sub model calculates activity coefficients for species in an aerosol phase based on the current aerosol phase composition [Marcolli2005]. The json object for this sub model has the following format :

{ "camp-data" : [
  {
    "name" : "my UNIFAC activity",
    "type" : "SUB_MODEL_UNIFAC",
    "phases" : [
      "some phase",
      "some other phase"
    ],
    "functional groups" : {
      "CH3" : {
        "main group" : "CH2",
        "volume param" : 0.9011,
        "surface param" : 0.8480
      },
      "CH2" : {
        "main group" : "CH2",
        "volume param" : 0.6744,
        "surface param" : 0.5400
      },
      "CH=CH" : {
        "main group" : "C=C",
        "volume param" : 1.1167,
        "suface param" : 0.8670
      }
    },
    "main groups" : {
      "CH2" : {
        "interactions with" : {
          "C=C" : -35.36
        }
      },
      "C=C" : {
        "interactions with" : {
          "CH2" : 86.02
        }
      }
    }
  },
  ...
]}

The key-value pair type is required and must be SUB_MODEL_UNIFAC. The key-value pair phases is also required, and its value must be an array of strings that correspond to valid aerosol phases. The key-value pair functional groups is also required, and must contain a set of key-value pairs whose keys are the names of UNIFAC functions groups, and whose values are a set of key value pairs that contain, at minimum:

• main group : a string that corresponds to a key in the main groups set.
• volume param : the floating-point volume parameter for this functional group.
• surface param : this floating-point surface parameter for this functional group. The last required key-value pair is main groups whose value must be a set of key-value pairs whose keys are the names of the UNIFAC main groups and whose values are a set key-pairs that contain, at minimum, interaction with whose value is a set of key-value pairs whose keys are the names of the other main groups and whose values are the floating-point interation parameters for that interaction. Each main group may contain up to one interaction with each other main group, and may not contain an interaction with itself. Missing interactions are assumed to be 0.0.

Species in the specified phase for whom acitivity coefficients will be calculated must contain a key-value pair UNIFAC groups whose value is a set of key value pairs that correspond with members of the functional groups set and whose values are the integer number of instances of a particular functional group in this species. There must also be a CHEM_SPEC_ACTIVITY_COEFF species with a key value pair chemical species whose value is the name of the chemical species. Both the chemical species and the activity coefficient must be included in any aerosol phase for which activities are being calculated. For the above example UNIFAC model, the following species would be valid and included in activity coefficient calculations:

{ "camp-data" : [
  {
    "name" : "my species",
    "type" : "CHEM_SPEC",
    "phase" : "AEROSOL",
    "UNIFAC groups" : {
      "CH3" : 4,
      "C=C" : 1
    }
  },
  {
    "name" : "gamma my species",
    "type" : "CHEM_SPEC",
    "phase" : "AEROSOL",
    "tracer type" : "ACTIVITY_COEFF",
    "chemical species" : "my species"
  },
  {
    "name" : "my other species",
    "type" : "CHEM_SPEC",
    "phase" : "AEROSOL",
    "UNIFAC groups" : {
      "CH3" : 2,
      "CH2" : 4
    },
  },
  {
    "name" : "gamma my other species",
    "type" : "CHEM_SPEC",
    "phase" : "AEROSOL",
    "tracer type" : "ACTIVITY_COEFF"
    "chemical species" : "my other species"
  },
  {
    "name" : "some phase",
    "type" : "AERO_PHASE",
    "species" : { "my species", "gamma my species",
                  "my other species", gamma my other species"}
  }
]}