diff --git a/diffusivityModel/Stockmayer/StockmayerI.H b/diffusivityModel/Stockmayer/StockmayerI.H
index 50dfe24..8f3f5c3 100644
--- a/diffusivityModel/Stockmayer/StockmayerI.H
+++ b/diffusivityModel/Stockmayer/StockmayerI.H
@@ -39,28 +39,28 @@ License
 
 inline Foam::scalar Foam::Stockmayer::Omega11(const scalar Tstar)
 {
-    const scalar a[6] = { 1.0548, 0.15504, 0.55909, 2.1705, 0.093193, 1.5 };
+    constexpr scalar a[6] = { 1.0548, 0.15504, 0.55909, 2.1705, 0.093193, 1.5 };
     return a[0] * power(Tstar, -a[1]) + power(Tstar + a[2], -a[3]);
 }
 
 
 inline Foam::scalar Foam::Stockmayer::Omega22(const scalar Tstar)
 {
-    const scalar b[6] = { 1.0413, 0.11930, 0.43628, 1.6041, 0.095661, 2.0 };
+    constexpr scalar b[6] = { 1.0413, 0.11930, 0.43628, 1.6041, 0.095661, 2.0 };
     return b[0] * power(Tstar, -b[1]) + power(Tstar + b[2], -b[3]);
 }
 
 
 inline Foam::scalar Foam::Stockmayer::f11(const scalar Tstar)
 {
-    const scalar a[6] = { 1.0548, 0.15504, 0.55909, 2.1705, 0.093193, 1.5 };
+    constexpr scalar a[6] = { 1.0548, 0.15504, 0.55909, 2.1705, 0.093193, 1.5 };
     return 1.0 + sqr(deltaij_)*(expon(a[4]/Tstar)-expon(-a[5]/Tstar))/(2 + 2.5*deltaij_);
 }
 
 
 inline Foam::scalar Foam::Stockmayer::f22(const scalar Tstar)
 {
-    const scalar b[6] = { 1.0413, 0.11930, 0.43628, 1.6041, 0.095661, 2.0 };
+    constexpr scalar b[6] = { 1.0413, 0.11930, 0.43628, 1.6041, 0.095661, 2.0 };
     return 1.0 + sqr(deltaij_)*(expon(b[4]/Tstar)-expon(-b[5]/Tstar))/(2 + 2.5*deltaij_);
 }