diff --git a/diffusivityModel/Particle/Particle.H b/diffusivityModel/Particle/Particle.H
index fefcef0..81492c7 100644
--- a/diffusivityModel/Particle/Particle.H
+++ b/diffusivityModel/Particle/Particle.H
@@ -123,13 +123,13 @@ public:
     // Member Functions
 
         // Access
-        inline const word& name();
+        inline const word& name() const;
 
-        inline scalar W();
+        inline scalar W() const;
 
-        inline scalar z();
+        inline scalar z() const;
 
-        inline Geometry geometry();
+        inline Geometry geometry() const;
 
         // Check
 
diff --git a/diffusivityModel/Particle/ParticleI.H b/diffusivityModel/Particle/ParticleI.H
index 7a5762d..9f76076 100644
--- a/diffusivityModel/Particle/ParticleI.H
+++ b/diffusivityModel/Particle/ParticleI.H
@@ -37,24 +37,28 @@ License
 // * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
 
 inline const Foam::word& Foam::Particle::name()
+    const
 {
     return name_;
 }
 
 
 inline Foam::scalar Foam::Particle::W()
+    const
 {
     return W_;
 }
 
 
 inline Foam::scalar Foam::Particle::z()
+    const
 {
     return z_;
 }
 
 
 inline Foam::Particle::Geometry Foam::Particle::geometry()
+    const
 {
     return geometry_;
 }