The piezoelectric constitutive equations in stress-charge form

are given by couple of equations (1) and (2). These equations

describe the relation between stress-charge form and stain-charge

form. The symbols are explained in Table .

Equations 1: stress-charge form

T = cE. S – e T. E

D = e . S + εS . E

Equations 2: strain-charge form

S = SE . T + dT . E

D = dT + εT.

Table . Piezoelectric constitutive equation symbols

T Stress

CE Elasticity matrix (rank 4 tensor)

S Strain

E Electric field

e Coupling matrix (rank 3 tensor)

D Electric displacement

ε Permittivity matrix (rank 2 tensor)

You can use the equation Sij=DijE

This is a very basic article. But I hope it helps,

https://www.americanpiezo.com/knowledge-center/piezo-theory/piezoelectric-constants.html