diff --git a/diffusivityModel/diffusivityModel/diffusivityModel.C b/diffusivityModel/diffusivityModel/diffusivityModel.C
index 6723ced..433a559 100644
--- a/diffusivityModel/diffusivityModel/diffusivityModel.C
+++ b/diffusivityModel/diffusivityModel/diffusivityModel.C
@@ -175,12 +175,10 @@ void Foam::diffusivityModel::calculateMuD
     const scalar pi = state.p();
     const scalar Ti = state.T();
     const scalar rhoQc2i = state.rhoQc2();
-    const scalarField &localY(state.Y());
-    const scalarField &localX(state.X());
 
     label ionStart = 0;
 
-    label neutralStart = 0;
+    label neutralStart = ions_.size();
 
     if (electron_.valid())
     {
@@ -189,63 +187,64 @@ void Foam::diffusivityModel::calculateMuD
         neutralStart = ionStart + ions_.size();
 
         // Electron - Electron
-        label idx = 0;
+        label iec = 0;
 
-        muI[0] = ecs_[idx].mu(pi,Ti,rhoQc2i);
+        muI[0] = ecs_[iec].mu(pi,Ti,rhoQc2i);
 
-        Dij(0,0) = ecs_[idx].D(pi,Ti,rhoQc2i);
+        Dij(0,0) = ecs_[iec].D(pi,Ti,rhoQc2i);
+
+        iec++;
 
         // Electron - Ions
-        idx = 1;
         forAll (ions_, J)
         {
             label j = J + ionStart;
 
             // Calculate Dij
-            Dij(0,j) = ecs_[idx].D(pi,Ti,rhoQc2i);
+            Dij(0,j) = ecs_[iec].D(pi,Ti,rhoQc2i);
             Dij(j,0) = Dij(0,j);
-            idx++;
+            iec++;
         }
 
         // Electron - Neutrals
-        idx = 0;
+        label ien = 0;
         forAll (neutrals_, J)
         {
             label j = J + neutralStart;
 
             // Calculate Dij
-            Dij(0,j) = ens_[idx].D(pi,Ti);
+            Dij(0,j) = ens_[ien].D(pi,Ti);
             Dij(j,0) = Dij(0,j);
-            idx++;
+            ien++;
         }
 
     }
 
     // Ions
-    label idx1 = 0;
+    label icc = 0;
     forAll (ions_, I)
     {
         label i = I + ionStart;
 
-        muI[i] = ccs_[idx1].mu(pi,Ti,rhoQc2i);
+        muI[i] = ccs_[icc].mu(pi,Ti,rhoQc2i);
 
-        Dij(i,i) = ccs_[idx1].D(pi,Ti,rhoQc2i);
+        Dij(i,i) = ccs_[icc].D(pi,Ti,rhoQc2i);
 
-        idx1++;
+        icc++;
 
         // Ion - Ions
         for (label J = I + 1; J < ions_.size(); J++)
         {
             label j = J + ionStart;
             // Calculate Dij
-            Dij(i,j) = ccs_[idx1].D(pi,Ti,rhoQc2i);
+            Dij(i,j) = ccs_[icc].D(pi,Ti,rhoQc2i);
             Dij(j,i) = Dij(i,j);
-            idx1++;
+            icc++;
         }
 
     }
 
-    label idx2 = 0;
+    label icn = 0;
     forAll (ions_, I)
     {
         label i = I + ionStart;
@@ -256,21 +255,21 @@ void Foam::diffusivityModel::calculateMuD
             label j = J + neutralStart;
 
             // Calculate Dij
-            Dij(i,j) = cns_[idx2].D(pi,Ti);
+            Dij(i,j) = cns_[icn].D(pi,Ti);
             Dij(j,i) = Dij(i,j);
-            idx2++;
+            icn++;
         }
     }
 
     // Neutrals
-    label idx = 0;
+    label inn = 0;
     forAll (neutrals_, I)
     {
         label i = I + neutralStart;
 
-        muI[i] = nns_[idx].mu(pi,Ti);
-        Dij(i,i) = nns_[idx].D(pi,Ti);
-        idx++;
+        muI[i] = nns_[inn].mu(pi,Ti);
+        Dij(i,i) = nns_[inn].D(pi,Ti);
+        inn++;
 
         // Neutral - Neutrals
         for (label J = I + 1; J < neutrals_.size(); J++)
@@ -278,9 +277,9 @@ void Foam::diffusivityModel::calculateMuD
             label j = J + neutralStart;
 
             // Calculate Dij
-            Dij(i,j) = nns_[idx].D(pi,Ti);
+            Dij(i,j) = nns_[inn].D(pi,Ti);
             Dij(j,i) = Dij(i,j);
-            idx++;
+            inn++;
         }
     }