Simplified scalar multiplication

src/elasticity/materials/GuccioneMaterial.cpp

@@ -128,10 +128,10 @@ double GuccioneBonetMaterial::q(const Tensor &E, const VectorField &f) const {
 
 Tensor GuccioneBonetMaterial::dq(const Tensor &E, const VectorField &f) const {
   VectorField Ef = E * f;
-  Tensor QE = 4.0 * a * (f * Ef) * Product(f, f);
-  QE += 4.0 * b * sym(Product(Ef, f));
-  QE += 4.0 * c * E;
-  return 2*QE;
+  Tensor QE =  a * (f * Ef) * Product(f, f);
+  QE += b * sym(Product(Ef, f));
+  QE += c * E;
+  return 8.0*QE;
 }
 
 Tensor GuccioneBonetMaterial::ddq(const Tensor &E, const VectorField &f, const Tensor &H) const {