I am new to MSC Marc/Mentat Software, and I’m working on a coupled thermo-mechanical analysis of a composite cube. I want to correctly define the boundary conditions to allow thermal deformation while avoiding rigid body motion.

I want to apply these boundary conditions:

1. Nodes on the Z = 0 (XY) plane: constrained in X and Y directions

2. the planes that are parallel to x, y and z=0 keep planar and remain parallel to their original positions when in deformation

How can I implement these properly in MSC Marc/Mentat without over-constraining the model?