Piezoelectric equation

The constitutive equation of piezoelectric materials reflects the relationship between elastic variables (stress T, strain S) and electrical variables (electric field E, electrical displacement D).In other words, the piezoelectric equation takes into account both the mechanical and electrical properties of the piezoelectric elements and their mutual coupling effects.
The first kind of piezoelectric equation:

S^E - Matrix of elastic compliance coefficient when electric field E=0 (or constant)
ε^T- This is the dielectric constant matrix at T=0
d - Piezoelectric strain coefficient matrix
d_t - This is d transpose