To plot/compute site occupancies with WERAMI it is neccessary to formulate a rule that relates the bulk composition to the site occupancy (this is always possible). For example suppose we want the site fraction of Na on the A site (Z(Na,A)) of an amphibole model with endmember site occupancies as follows: Site: A M1 M2 M4 T1 Mutliplicity: 1 3 2 2 4 1 tr Vac Mg Mg Ca Si_Si 2 ftr Vac Fe Fe Ca Si_Si 3 ts_dqf Vac Mg Al Ca Al_Si 4 fts Vac Fe Al Ca Al_Si 5 parg_dqf Na Mg Mg_Al Ca Al_Si 6 fparg Na Fe Fe_Al Ca Al_Si 7 gl Vac Mg Al Na Si_Si 8 fgl Vac Fe Al Na Si_Si From inspection of the endmember site occupancies we deduce: Z(Na,A) = 2*[Z(Al,T1) - Z(M,M2)] where M = Fe + Mg then Z(Al,T1) = 1 - Z(Si,T1) Z(Si,T1) = (n(SiO2) - 4)/4 Z(M,M2) = ([n(MgO) + n(FeO)] - 3)/2 and substituting these last three relationships into the first we obtain the desired "rule" (you may want to check my math, as I haven't): Z(Na,A) = 7 - n(MgO) - n(FeO) - 1/2 n(SiO2) which can be evaluated in WERAMI. The only problem in getting this composition from WERAMI is the constant "7". A trick for including such constant is include a component in the composition that is in fact constant, and multiply the amount of this component by a factor that gives the constant; for example, in this amphibole model n(H2O) = 1, therefore n(H2O)*7 = 7). The WERAMI dialog to define the above expression for Z(Na,A) is: Select a property: 1 - Specific Enthalpy (J/m3) 2 - Density (kg/m3) 3 - Specific heat capacity (J/K/m3) 4 - Expansivity (1/K, for volume) 5 - Compressibility (1/bar, for volume) 6 - Weight (%) of a component 7 - Mode (Vol, Mol, or Wt proportion) of a phase 8 - Composition (Mol or Wt) of a solution 9 - Grueneisen thermal ratio 10 - Adiabatic bulk modulus (bar) 11 - Adiabatic shear modulus (bar) 12 - Sound velocity (km/s) 13 - P-wave velocity (Vp, km/s) 14 - S-wave velocity (Vs, km/s) 15 - Vp/Vs 16 - Specific entropy (J/K/m3) 17 - Entropy (J/K/kg) 18 - Enthalpy (J/kg) 19 - Heat Capacity (J/K/kg) 20 - Specific mass of a phase (kg/m3-solid) 21 - Poisson ratio 22 - Molar Volume (J/bar) 23 - Chemical potentials (J/mol) 8 Enter solution or compound name (left justified): Amphibole Compositions are defined as a ratio of the form: Sum {w(i)*n(i), i = 1, c1} / Sum {w(i)*n(i), i = c2, c3} n(j) = mole proportion of component j w(j) = weighting factor of component j (usually 1) How many components in the numerator of the composition (<16)? 4 Enter component indices and weighting factors for the numerator: 1 - H2O 2 - MGO 3 - AL2O3 4 - SIO2 5 - K2O 6 - CAO 7 - FEO 8 - NA2O 1 7 2 -1 7 -1 4 -0.5 How many components in the denominator of the composition (<12)? Enter zero to use the numerator as a composition. 0 The compositional variable is: 7.0 H2O -1.0 MGO -1.0 FEO -0.5 SIO2