Hi, In papers discussing the physical properties of semiconductors, I have found that they have calculated the piezoelectric coefficient as the ratio between the polarization and the strain in a linear regime (which produces e): a) I think in experiment we first insert an electric field then we calculate the piezoelectric coefficient (d). Therefore, I would like to know how we can first insert an electric field and then calculate the piezoelectric constant theoretically. (I mean how can we have d and e together?) Or how can we have e and then we calculate the electric field consequently. b) In some codes we can calculate the charge transport and as I know they give I-V curves. I wanted to know if it is possible to have the electric potential (the voltage) if we put mechanical stress on the system we are calculating in such computational codes? is there a relation between the charge transport and piezoelectricity in atomic scales and in theoretical point of view?