Program to calculate Activity Coefficient mix by UNIQUAC (Universal quasi-chemical) Equation

Z =lattice coordination number set equal to 10.

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A first algorithm to calculate and the second for i as following:-

Excel Visual Basic Application (VBA) Code.

Option Explicit

Function UNIQUAC(T As Double, X As Range, aij As Range, ri As Range, qi As Range)

Dim N As Integer, i As Integer, j As Integer, k As Integer

Dim L() As Double, Fayi() As Double

Dim Theti() As Double, tij() As Double, SUMA As Double, SUMB As Double, SUMC As Double, SUME As Double

Dim GAMMA() As Double, SUMF As Double, SUMG As Double, ANSW() As Double, GC() As Double, GR() As Double

N = X.Count

ReDim L(N) As Double, Fayi(N) As Double, Theti(N) As Double, tij(N, N) As Double, GAMMA(N) As Double

ReDim ANSW(1 To N) As Double, GC(N) As Double, GR(N) As Double

For i = 1 To N

SUMA = 0: SUMB = 0

For j = 1 To N

tij(i, j) = Exp(-aij(i, j) / T)

SUMA = SUMA + ri(j) * X(j)

SUMB = SUMB + qi(j) * X(j)

Next j

Theti(i) = qi(i) * X(i) / SUMB

Fayi(i) = ri(i) * X(i) / SUMA

Next i

For i = 1 To N

SUME = 0: SUMF = 0: SUMG = 0

For j = 1 To N

SUMC = 0

For k = 1 To N

SUMC = SUMC + Theti(k) * tij(k, j)

Next k

L(j) = 5 * (ri(j) - qi(j)) - (ri(j) - 1)

SUMF = SUMF + X(j) * L(j)

SUME = SUME + Theti(j) * tij(i, j) / SUMC

SUMG = SUMG + Theti(j) * tij(j, i)

Next j

You Can Use Application.Ln() Instead WorksheetFunction.Ln()

GC(i) = WorksheetFunction.Ln(Fayi(i) / X(i)) + 5 * qi(i) * WorksheetFunction.Ln(Theti(i) / Fayi(i)) _

+ L(i) - (Fayi(i) / X(i) * SUMF)

GR(i) = qi(i) * (1 - WorksheetFunction.Ln(SUMG) - SUME)

GAMMA(i) = GC(i) + GR(i)

ANSW(i) = Exp(GAMMA(i))

Next i

UNIQUAC = WorksheetFunction.Transpose(ANSW)

End Function