Mooney-Rivlin's model of a compressible hyperelastic material is described by the strain energy function $$\psi=\psi_v+\psi_d,\quad \psi_v=\frac{1}{2}\kappa(J-1)^2,\quad \psi_d=C_1(\bar I_1-3)+C_2(\bar I_2-3),$$ where $C_1,C_2$ are the material model's parameters, $\kappa$ is the bulk modulus, $J=\det\mathbf{F}$ is the determinant of the deformation gradient $\mathbf{F},$ and $$\begin{array}{lll} \bar I_1=J^{-2/3}I_1, & I_1=C_{11}+C_{22}+C_{33}, \\ \bar I_2=J^{-4/3}I_2, & I_2=\det\left(\begin{array}{ll}C_{11}&C_{12}\\C_{21}&C_{22}\end{array}\right)+\det\left(\begin{array}{ll}C_{11}&C_{13}\\C_{31}&C_{33}\end{array}\right)+\det\left(\begin{array}{ll}C_{22}&C_{23}\\C_{32}&C_{33}\end{array}\right)\end{array}$$ are the first and second invariant of the modified Cauchy-Green deformation tensor $\mathbf{\bar C}=J^{−2/3}\mathbf{C},$ where $\mathbf{C=F}^\mathrm{T}\mathbf{F}.$

PMD does not support calculations with a zero elastic modulus $E,$ therefore, it is necessary to transform the material parameters first. Given the shear modulus as $\mu=2C_1,$ we can determine the tangential elastic modulus in the non-deformed state and the Poisson ratio using formulas $$E=\frac{9\kappa\mu}{3\kappa+\mu},\quad \nu=\frac{3\kappa-2\mu}{2(3\kappa+\mu)}.$$

Material quantities are defined in the file name.i2, where the parameter $C_2$ is entered on the 11th position of the MP batch:

The model is activated by the key $\mathtt{KLARG}=5$ in the file name.iP.