MooneyRivlinDensity: Correct comment

dune/elasticity/materials/mooneyrivlindensity.hh

@@ -68,8 +68,8 @@ public:
        There are three Mooney-Rivlin-Variants:
        ciarlet: W(F) = mooneyrivlin_a*(normF)^2 + mooneyrivlin_b*(normFinv)^2*detF + mooneyrivlin_c*(detF)^2 -
                        ((dim-1)*mooneyrivlin_a + mooneyrivlin_b + 2*mooneyrivlin_c)*ln(detF)
-       log:     W(F) = \sum_{i,j=0}^{i+j<=n} mooneyrivlin_ij * (I1 - 3)^i * (I2 - 3)^j + mooneyrivlin_k * ln(det(F))
-       square:  W(F) = \sum_{i,j=0}^{i+j<=n} mooneyrivlin_ij * (I1 - 3)^i * (I2 - 3)^j + mooneyrivlin_k * 0.5 * (det(F) - 1)
+       log:     W(F) = \sum_{i,j=0}^{i+j<=n} mooneyrivlin_ij * (I1 - 3)^i * (I2 - 3)^j + mooneyrivlin_k * ln(det(F))^2
+       square:  W(F) = \sum_{i,j=0}^{i+j<=n} mooneyrivlin_ij * (I1 - 3)^i * (I2 - 3)^j + mooneyrivlin_k * 0.5 * (det(F) - 1)^2
        
        For log and square: I1 and I2 are the first two invariants of C (or B), multiplied with a factor depending on det(F):
        I1 = (det(F)^(-2/dim)) * [ first invariant of C ]