What is the back-end for Piezoelectric stack actuator in simulink?

Hello Everyone, Piezoelectric stack actuator acts as a capacitor below resonance frequency. In simulink, there is a block called Piezostack. There are certain parameters as well. However, the information about this block does not justify how the back-end programming has been developed for this block? Is this simply a capacitor in the back-end? Thanking you in anticipation.